I am an experienced jam-maker, but I’ve never canned tomatoes or tomato sauce. This year, thanks to two “rogue” tomato plants (one apparently Roma style, one generic smallish red tomato) in addition to the heirloom seedlings I planted, I have plenty of tomatoes and would like to try making my own sauce, using my water-bath canner. I’ve looked at recipes online and in books, and I understand that I’ll have to add some bottled lemon juice to get the acidity high enough for safety. I’d appreciate any other advice or tips from experienced tomato-sauce canners out there. Thanks!
I hate to break it to you, but you only need to freeze it. Get some 8oz/16oz canning jars and put your sauce/juice into them. Simple and fast. We have been doing this with our surplus tomatoes for years.
I could do that, but then I wouldn’t have the satisfaction of boiling any potential bad buggies to death and beyond!
Yesterday I canned two pints and three half-pints of “Crushed tomatoes with no added liquid” from a USDA recipe. It turns out both of my “rogue” tomato varieties are perfect for canning, meaty without a lot of seeds or juice.
My mom struggled with this for many years. She was never able to come up with a spice/herb blend she liked that could stand up to the canning. It would taste great before canning but always turned bitter or bland after. She eventually gave up canning ready to use, flavored sauce and just canned plain, crushed tomatoes.
I’d probably simmer the plain tomatoes with a geberous pinch of salt and sugar, reduce them a bit. Add a tablespoon to 2 tablespoons of redwine vinegar to every small jar of tomatoes. Boilk to seal for around 12 minutes.
Do not add lemon juice for the acidity. I made that mistake a four years ago. Nobody could stand the flavor of the sauce, because it had a strong lemon flavor. Use vinegar if you have to acidify the sauce. I used lemon because the site recommend it over vinegar as an acidifier. Too bad they didn’t consider the taste as important. I hate that site for ruining what would have been great sauce.
You’re supposed to immediately cook down tomatoes that you prepare to prevent the enzymes from making a chemical that causes separation of solids and liquid in the jar. Bruising of the cells starts the reaction so just slicing and crushing them starts it. Add the chunks as you slice up the tomatoes into already heated sauce in the pan. Don’t slice up all the tomatoes and then turn on the heat.
This seems like a lot of trouble to go to - I’ve made tomato sauce for years and I just freeze it. It’s cooked, so there are no bacteria to worry about, and it keeps frozen for months.
Another vote for “Freeze it.” That’s what we do with the excess from out plants. That which doesn’t get guilted out of us by family, neighbors, random passers-by, etc. 
I use the recipe in Barbara Kingsolver’s Animal, Vegetable, Miracle, and the sauce is a HUGE hit with everyone I’ve ever given it to.
You can print out this PDF with it, but here it is in plain text.
The point of this recipe is to make a large amount at one time, when tomatoes are in season. If you’re canning it, stick closely to the recipe; adding additional fresh vegetables will change the pH so it’s unsafe for water-bath canning. If you’re freezing it, then it’s fine to throw in peppers, mushrooms, fresh garlic, whatever you want. This recipe makes 6-7 quarts – you can use a combination of pint and quart canning jars or freezer boxes.
10 quarts tomato puree (about 30 lbs. tomatoes)
4 large onions, chopped
1 cup dried basil
½ cup honey
4 tbs. dried oregano
3 tbs. salt
2 tbsp ground lemon peel
2 tbsp. thyme
2 tbs. garlic powder (or more, to taste)
2tbs. dried parsley
2 tsp. pepper
2 tsp cinnamon
½ tsp nutmeg
Soften onions in a heavy 3-gallon kettle – add a small amount of water if necessary but no oil if you are canning (very important!). Add pureed tomatoes and all seasonings, bring to a boil, and simmer on low heat for two to three hours until sauce has thickened to your liking. Stir frequently, especially toward the end, to avoid burning. Meanwhile, heat water in canner bath, sterilize jars in boiling water or dishwasher, and pour boiling water over jar lids.
bottled lemon juice or citric acid – NOT optional!
Add 2 tbsp of lemon juice OR ½ tsp. citric acid to each quart jar, (half that much to pint jars). This is ensures that the sauce will be safely acidic. When the sauce is ready, ladle it into the jars leaving ½ inch headspace. Put jars into canner and boil for 35 minutes. Remove, cool, check all seals, label and store for winter.