Wash tomatoes thoroughly. Cut out the stem and any defects or blemishes. Some people also peel the tomatoes, but I never do and we honestly have not noticed the peelings at all- and I’m even funny about textures like that in food. I figure why bother with the extra step, plus it’s a bit healthier too!
Slice tomatoes into about ½ inch thick slices, then dice them into whatever size you want. I love using my Vidalia Chop Wizard for this!
Place diced tomatoes into a clean canning jar- a funnel makes this super easy. Gently shake jar to settle tomatoes so that you can fill it completely. The tomatoes should be packed tightly in order to produce enough juice. It won't hurt if you press down on them a bit to get the jar packed full- in fact, this is probably going to be necessary. The jar should be full to the base of the neck.
Add salt (½ tsp. per pint and 1 tsp. per quart) and bottled lemon juice (1 Tbsp. per pint and 2 Tbsp. per quart). Wipe rim of each jar with a damp cloth to remove any tomato residue that may be there. (If there is even a slight bit of tomato juice on it, it may not allow it to seal properly.)
Once you have 7 jars filled, place 7 metal canning lids in a small pan. Cover with water; bring to a boil. Once the water boils, use a fork or lid lifter to lift the jar lids out of the water- be careful not to burn yourself!- and place them on the jars. Secure each lid with a jar band/ring. (Heating the lids softens the rubber, allowing for a better seal.)
Place 7 jars in canner. Fill with enough hot water to almost cover the jars. Turn the burner on medium high heat. Once water starts to boil, reduce heat slightly and process for 45 minutes, making sure the water is boiling gently and steadily the whole time. (You may need to adjust heat to keep the boil going nicely, but really, as long as it is boiling, you are fine.)
After processing for 45 minutes, turn the burner off. Remove jars using jar lifter- you may want to have a dishrag in your other hand to catch any hot water that drips from the jars as you remove them- and place on an old towel, blanket or another padded surface. (This is to protect your counter from the super hot jars.) Allow at least a little bit of air space around each jar, making sure not to have jars close enough to touch. Do not move until jars are completely cool.
Jars should seal as they cool and you will typically hear a snap or pinging sound as the vacuum seal is formed. Lids will be slightly concave when sealed. To test the seal, once jar has totally cooled, lightly tap the center of the cooled jar lid. If it is firm and does not move, it should be sealed. If it pushes in, it didn’t seal properly. You can still use unsealed jars, just put them in the refrigerator and use them as soon as possible.
After jars are completely cool, you can remove the rings. Jars should be wiped clean before storing them.
1 pint of canned diced tomatoes is equivalent to 1 (15 oz.) can of diced tomatoes.