You'll need:
Farm-fresh Roma tomatoes, a bushel or so
14 quart (1 L) Mason jars (if nobody eats any tomatoes before you start canning, you might need 15)
14 (or 15) snap lids and rings
And per jar:
Sprinkle of kosher salt (optional)
1/2 t citric acid or 2 T bottled lemon juice
Having a home near Leamington, Ontario is absolutely GLORIOUS in tomato season. Tomato fields start glowing red as the crop ripens. And there are so many farm stands, like real actual farm stands. (The St. Jacobs Farmers Market has taught me to always ask where the produce I'm buying comes from. The year-round stalls selling berries super cheaply, for example, aren't likely to be local berries, even if you're buying at the height of the local berry season. I love the St. Jacobs Farmers Market, and there are a lot of actual farmers there. But you gotta ask. Anyway...)
So when I bought these tomatoes, I asked the elderly Italian-accented lady where they came from. She gestured toward the house, and said, "the field outbacka the building!" Sure enough, just beyond lay acres of glowing red tomatoes. That's local!
Directions for canning:
Make sure you have plenty of ice or very cold water. Follow your pressure canner's instructions to double check that your pressure canner is ready to go.
Wash your jars in hot soapy water and rinse well. I didn't bother to pre-sterilize them because pressure canning will take care of that.
Rinse your tomatoes well and rub off any bits of field dirt. These were pretty pristine, but if there's been a recent rain they might be a bit muddy.
Take a sharp paring knife and cut an X into each tomato. (Not super necessary, but helpful.)
Put a good-size pot of water on to boil. Put ice and/or very cold water in a large bowl or your clean sink.
Working with about a half-dozen tomatoes at a time, put them in the boiling water for about a minute, then remove them to the ice bath.
7. Once they've cooled, their skins will slip off quite easily, especially if you've given them a starting place with that X.
8. Core each tomato and put it into another bowl. Try not to be too rough at this point because you don't want to squeeze too much of the juice out.
9. Prepare your jars with either citric acid or lemon juice. I do 7 jars at a time because that's how many quarts my canner will hold. My first batch used citric acid. My second used lemon juice because I ran out of citric acid.
10. Heat water in a small pot and put your snap lids in there. They don't have to come to a boil. It's just to soften them a smidge to help them seal.
11. Once you have a big bowl of prepared tomatoes, start packing your jars. Basically you're just squashing tomatoes by the handful into the jar. Pack as many as you can in (squish them down to release the juice), leaving about 1/2 inch head space.
12. "Bubble" each jar with a skewer or chopstick to release any trapped air. Wipe each rim with a clean damp paper towel. Place a heated snap lid down and screw the ring on finger tip tight.
13. Add hot water to your pressure canner. Mine requires 3 quarts; check your instructions to be sure for yours.
14. Load up the canner and close it, following manufacturer instructions. (As many times as I've used my pressure canner, I also reread the instructions. I don't know. The whole possibility of explosion thing makes me nervous, I guess. But I do love it.)
15. At sea level, which I basically am, tomatoes take 25 minutes at 10 pounds pressure. While your first batch is on and then cooling, you might as well get the second batch ready.
So worth it! You can totally do tomatoes safely and effectively by water bath canning as well. Follow all the directions the same, up to step 12. Just boil the cans in the water bath for 85 minutes. I opted for pressure canning this time around because we have no air conditioning so the less boiling, the better.