I have a recipe that I personally researched at the University of Georgia.  Unfortunately, they have not yet published it.

Per pint jar: 1 part Roma tomatoes (only Roma were researched) approx 8 oz. by weight (Boil 1 minute, then plunge in cold water to loosen skin.  Slip skins off.). Cut into 1/2 inch pieces or smaller.
1 part any combination of onions and peppers (sweet or hot) approx 8 oz. by weight. Dice into 1/4 inch pieces.
Up to 1 tablespoon total of dry spice. We used 1/4 tsp salt and in one batch 1/4 teaspoon cumin.

Heat in a saucepan for 1 minute.  Add 1/3 cup lime or lemon juice into a pint jar.  Fill with cooked salsa to 1/2 of top.  Heat in a boiling water canner for 20 minutes.