Canning method
Wash fresh tomatoes. Scald 3 minutes in boiling water. Dip into cold water. Cut out core, remove skins and chop coarsely. If using canned tomatoes, do not drain liquid. For this recipe, I used the canned diced petite tomatoes.
Combine tomatoes, vinegar and Salsa mix in a large pot and bring to a boil. Stir occasionally. Reduce heat and simmer 10 minutes. Stir occasionally. Pour hot salsa into clean, sterilized pint canning jars, leaving 1/2-inch headspace, wipe rim clean with a damp cloth.
Place hot lid on hot jar, screw band down evenly and firmly. Process in a boiling water bath for 40 minutes. After processing, remove jars and set them upright on a towel in a draft-free area to seal.
After cooling, test each jar for a seal by pressing on the center of the flat, if it does not flex, the jar is sealed.
Processing: As published by Mrs. Wages: "Process in a boiling water bath for 40 minutes" (boiling water bath canner) - 40 minutes.