baked oats green chile chicken enchiladas chow mein bakery-style butter cookies

copyright jennifer yu © 2004-2023 all rights reserved: no photos or content may be reproduced without prior written consent

cray cray

Recipe: diced tomatoes (canning)

More tomatoes? Yes, yes dammit. MOAR TOMATOES. What on earth did you think was going to happen with 77 pounds of tomatoes? We’re not kidding around here, because you know… winter is coming.

rain, mist, and temps in the 40s off my deck

Reports began to stream in Wednesday morning from the local Colorado ski hills – snow. A lovely dusting of white on the high peaks in some places with up to ten inches predicted for other places. Of course, the sun will return and the air will warm again, but the skiers and riders and general winter enthusiasts are rejoicing and hoping for a good (read: powdery) winter. Meanwhile, my parents are preparing to migrate back to warmer climes soon, so we met up for a delightful dinner at The Kitchen Upstairs.

my parents dig the boulder food scene

what’s left of the appetizers, because we ate them up

black pepper gnocchi with prosciutto and roasted plums

lamb meatballs on creamy polenta

pappardelle with pork

Unlike some places that continue to act like summer well into autumn, Colorado understands that it is time to move on. The fall colors are rolling about a week ahead of schedule and it’s crunch time for me – trying to can as much of the remaining summer produce as possible before I hit the road for the fall shoot. I feel like one of those pika in the mountains, scurrying about gathering foods for the winter. Ever read the book Frederick by Leo Lionni? It’s about a little mouse who sits in the sun all day while the rest of the mice are busy building stores for winter. Everyone is like, “Dude, you so lazy!” But come winter, Frederick unleashes his talent for awesome and everyone is all, “I totally get why you were such a slacker this summer!” I am not Frederick. I’m the other mice.

mice activities

I met up with a couple of my gal pals, Wendy and Ellen of Helliemae’s Salt Caramels, for a massive tomato canning session at the Helliemae’s kitchen in Denver this week. You know you have good friends when they allow you to go all OCD on them in the kitchen. We processed almost 60 pounds of tomatoes for dice and sauce. So yeah, you get another tomato recipe because I’m seeing tomatoes in my sleep right now. It is tomato-fest. There will be more too, so if you’re a ‘mater-hater, then just come back on Monday…

organic slicing tomatoes (seconds)

some bottled lemon juice

and beautiful weck jars

Diced tomatoes are pretty straightforward. Core them, then turn them around and score them (shallow) with a small, sharp knife. Put an X on the base to facilitate peeling the skins off.

remove the core on the stem end

x marks the spot

it goes quickly

Before you attempt to peel the skins off, it helps to cook the tomatoes in boiling water for a minute or two. Then plunge the tomatoes into an ice water bath. If the skins didn’t start to pull back already, they’ll likely start once in the bath. Pull the skins off with your fingers. They should release easily, although I found a few stubborn spots that I skinned with my pairing knife. Then dice the naked tomatoes and put it all (seeds, juice, and tomatoes) in a large pot.

icy bath after boiling



Simmer the tomatoes down until the liquid has thickened to your desired consistency. This takes about a half hour and will go faster if you cook the tomatoes in a pot with a larger surface area (physics). Pour a tablespoon of bottled lemon juice into each of your prepared pint jars. If you are using smaller jars or larger jars, scale the amount of lemon juice accordingly (math). Now, I love fresh-squozen lemon juice as much as the next guy, but it’s important to use bottled lemon juice because the acidity is consistent whereas it can vary wildly from one lemon to the next. The lemon juice is added for the acidity and not flavor (chemistry).

cook it down

lemon juice

ladle the diced tomatoes into the jars

Process the jars accordingly and now you have diced tomatoes that will taste like summer in the dead of winter! I go through a lot of tomatoes for soups and stews and sauces. This will be the first year I’ll have canned my own. They are organic, they are in BPA-free jars, I know exactly what is in them, and the tomatoes were grown not more than 25 miles from my house. Gold star!

pints of diced tomatoes

Diced Tomatoes (Canned)
[print recipe]
from Food in Jars by Marisa McClellan

6 lbs. (2.7 kg) Roma or paste tomatoes (I used organic slicing tomatoes)
1/4 cup (60 ml) bottled lemon juice, divided

Prepare the tomatoes: Set a large pot of water over high heat to boil. Core the tomatoes and score the bottom of each tomato with a shallow X. Get a large bowl and fill it with ice and water (ice water). When the water in the large pot comes to a boil, add some of the tomatoes and cook for 1-2 minutes. Fish the tomatoes out of the pot with a slotted spoon and immediately immerse them in the ice water bath to cool and to stop the cooking. When the water in the large pot returns to a boil, repeat with the next batch of tomatoes. As soon as the tomatoes have cooled enough to be picked up, start peeling the skins off (this should be easy). Large dice the tomatoes and place them in a large pot with all of the juices and seeds. Set the tomatoes on high heat and bring to a boil, then reduce and let simmer for 30-35 minutes, stirring on occasion until the liquids have thickened.

Notes: I have made this recipe using only Weck jars. The Weck site has some nice canning instructions if you are using their jars, which differ slightly from the standard instructions for canning with Ball-style jars. I canned 4 1-pint Weck jars from this recipe. Also, use bottled lemon juice rather than fresh lemon juice, because the acidity varies from lemon to lemon, but bottled juice has a more consistent acidity which is necessary for safety reasons in this recipe.

Canning the tomatoes: Ready the boiling water bath and the clean (washed with soap and water) jars you plan to use for canning. Check your jars and lids for nicks or cracks – don’t use them if they have any because it could jeopardize creating a good seal. If using standard Ball or similar style jars, it helps to put them in the pot you plan to use for canning and fill them (and the pot) with water, then bring to a boil. Keep the jars at a simmer (180°F) until they are ready to use. Place the lids in a small saucepan with enough water to cover them and set to a simmer over low heat (high heat can compromise the gummy seal material). If using Weck jars, you only need to sterilize your jars and glass lids if they will be processed for less than 10 minutes. Place the rubber rings in a small saucepan of water and bring to a boil for 2-3 minutes then leave them in the hot water until you are ready to use them.

Place 1 tablespoon of lemon juice in each pint jar. Fill each jar with hot diced tomatoes, leaving 1/2-inch headspace. Gently tap the jars on a padded surface (the towel on your workplace is a good place) to dislodge any air pockets.

Use a cloth to wipe the rims clean and apply the lids and rings of the Ball-style jars to fingertip tight (just tightened with fingertips – not super tight). If using Weck jars, place the rubber rings on the glass lids and set them on the jars. Secure the lids with two canning clamps for each jar – 180° from each other (across from each other). Set the jars in your canning bath (either on a jar rack or a makeshift cooling rack – just be sure they are not set directly on the bottom of the pot) and check that there is at least 1-2 inches of water above the lids of the jars – if not, add more water. Once the pot has returned to a boil, process for 35 minutes if you are at an altitude of sea-level to 1,000 feet above sea level (asl). For 1,001 to 3,000 feet asl, add another 5 minutes to the 35 minute processing time. For 3,001 to 6,000 feet asl, add 10 minutes to the 35 minute processing time. For 6,001 to 8,000 feet asl, add another 15 minutes to the 35 minute processing time. And finally, for 8,001 to 10,000 feet asl (that’s me!) add an additional 20 minutes to the 35 minute processing time for a total of 55 minutes.

When the tomatoes are done processing, remove them from the canning bath and place them on a towel-lined countertop to let them cool. Don’t mess with them! For the metal lids, you may hear the “ping” of the seals forming as the center of the lid gets sucked down. There will be no pinging of the Weck lids, but you may notice the tongue of the rubber band pointing down (this is good). Let the jars cool for 24 hours. Remove the bands or clamps and lift the jar an inch or so off your work surface (carefully – in case the seal is bad and breaks) by the lid. If the seal is good, it should hold. If a seal fails, you can always reprocess the tomatoes in a clean jar with new lid (Ball) or new gasket (Weck)! Also, any jar with a bad seal can be stored in the refrigerator. Store the jars in a cool, dark location for up to a year (take the clamps and rings off).

20 nibbles at “cray cray”

  1. Kristin says:

    Gotta tell you, the jars alone are enough to make we want to can!

  2. Beth says:

    I canned 25 pounds of tomatoes last Saturday, I can’t imagine doing 77! They look gorgeous in those jars.

  3. Connie says:

    That is quite a feat to dice 77 pounds of tomatoes! They look so luscious and vibrant.

  4. Margie says:

    All winter long we will be scrumptiously spoiled by your bounty…all winter long…:)

    (I am currently taking a nap in your honor.)


  5. Eileen says:

    Yay canning! I made a batch of tomato sauce almost exactly like this (I mean, besides being sauce instead of diced tomatoes) just this last weekend, and I’m totally going to keep doing it every weekend until the tomatoes run out. :)

  6. Cooking with Michele says:

    Gotta tell you that I hate the whole canning process – but I do love having local tomatoes saved for the winter. So this year I self-picked over 100 pounds of them from my CSA farm and froze about 2/3 of them (clean, core, rough chop – didn’t even bother to skin them) in reusable containers and made the best sauce (which I also froze) from the other third. I now have 67 pints of tomatoes to use in recipes and about 15 jars of incredible organic sauce. I’m ready for winter now!

  7. Duaba says:

    LOL love the frederick reference!

  8. Amy says:

    I have been reading your blog for a few years, love it! I’ve been wanting to put some tomatoes up all summer, but summer got in the way and now school has started. We homeschool and I now have the perfect way to incorporate canning tomatoes with school! Can’t wait to see what other tomato lessons, I mean recipes you have.

  9. sharon kitchens says:

    Your photos are gorgeous. Miss you!!! xo

  10. laura h says:

    But what of us who don’t have access to a commercial kitchen. :(

  11. jenyu says:

    Kristin – yeah, the Weck jars are so awesome :)

    Beth – 77 is muuuch easier when you have three people working on it in a big kitchen!

    Connie – well, in all honesty, it was 58 pounds at Helliemae’s commercial kitchen which we made into diced tomatoes and also tomato sauce. I use the remaining 20 pounds to make more tomato jam and tomato sauce at home. But the tomatoes are just fabulous.

    Margie – thank you, I needed that! ;)

    Eileen – I wish!! I have to go on travel and so rushed to process all my tomatoes now.

    Cooking w Michele – I totally would too if I were down in Denver. It’s still hot there! Much better up here in the mountains since it really started cooling off. You’re a rockstar for picking 100 pounds!! xo

    Duaba – oh yay! Someone knows what I’m talking about :) I thought I was the only one who read that as a kid.

    Amy – awesome :)

    sharon – you’re sweet. I miss you too! Are you back in Maine w your new puppers? xo

    laura h – I did this batch in my home kitchen. You don’t need a commercial kitchen to do this (I just happened to process a huge batch with Ellen and Wendy at Ellen’s commercial kitchen).

  12. Jessica says:

    I made some homemade sauce this weekend from our tomato plants but it was horribly acidic. I suppose I should have put the lemon juice in there, or would that make it worse? Also, I am so happy to see that you use the seeds, I’ve been removing all of mine along with the skins!

  13. Kathy Swanson says:

    Love the Weck jars. We didn’t have those when I was doing lots of canning for our family.

  14. Shut Up & Cook says:

    Absolutely gorgeous, as always!

    I think I’ve got some slow roasting of tomatoes in my future this Friday evening as I’ve got loads of them to save for winer!

  15. Nan says:

    It’s cooling off here too… My crazy organic garden has produced so many tomatoes this year that I believe I’ve canned every single day for the past month. Seriously. My canners have taken up what seems to be permanent residence in my kitchen for the duration. I use citric acid powder in lieu of the lemon juice. It’s very consistent and easily stored. Available in most Indian food markets.

    Because my garden is organic, I don’t bother peeling my tomatoes prior to canning. I just wash them really well, core them, cut off the blossom end and plop them into the jars along with a little (very little) salt, citric acid. On goes the lid and process them (Pressure can these). When I want to use them, I simply open up the jar, drop in the submersion blender and give them a whirr. Perfectly red, beautiful tomato sauce — much easier than peeling — especially the Romas.

    You can freeze whole washed tomatoes in freezer bags. When you want to use them, just run a little hot tap water over the frozen tomato and the skin slips right off and they are ready to go.

  16. jenyu says:

    Jessica – the lemon juice is to maintain an acidity that will prevent botulism, it’s not for flavor – so yes, please add the lemon juice :) I posted a tomato sauce recipe too and I really like it. Maybe try that one?

    Kathy – I am obsessed with Weck jars! :)

    Shut Up & Cook – I want to do that too! Except I think I’ve missed the end of tomato season *sigh*

    Nan – thanks for the info.

  17. Alison says:

    Jessica, you can add sugar to tomato products (per this is OK). Or, when you’re heating up your sauce to eat it, add some diced or grated carrots to sweeten it a bit. You can’t add carrots to a canning recipe before canning it, though.

    Most of the tomatoes I preserved this year ended up in the freezer because it was too hot to can! But I am about to can just a small amount of the last good tomatoes of the year.

  18. Canning; or, what I did with 40 lbs of tomatoes « Gluten Free Pumpkins says:

    […] the diced tomatoes, I followed use real butter’s directions. This was the only recipe I messed up this year. Seriously. And this is probably the […]

  19. linda harris says:

    I am allergic to lemons and any citric acid. I read that you can substitute vinegar. Is this true? I want to be safe and not end up sick, or worse, lose my tomatoes. Citric acid is in everything we eat. It makes me breaks out in hives. Thanks, Linda.

  20. jenyu says:

    linda – I don’t know, as I have never tried it before. My guess is that it should be okay as far as food safety goes, as long as your vinegar is a certain percentage acid which is what counts. I think the amount is small enough that it doesn’t really affect the flavor. Good luck!

leave a reply