Rinse tomatoes and dice them up.

Juice 1 or more lemons; add lemon juice to your jars, about 1/2 tsp. each (for pints).

Add filtered water.  You can also optionally use tomato juice for more flavor and/or add 1/2 tsp. of salt to each jar.  (I salted mine when cooking later.)

Cap the jars and process them in a water bath for 20 minutes (25 minutes for quart-size jars).  Now they are done!