The key to canning the freshest tomato salsa is doing so when the tomatoes are in peak season. Also be sure to find a canning recipe that is tried and true, because canning tomato salsa improperly can cause it to spoil. And peeling the tomatoes first is worth the effort. Canning tomato salsa is not the same as making it fresh to eat the same day. The skins will become tough and chewy once canned.
Pepper varieties can be mixed and matched in this recipe, but do not change total amount of peppers. The recipe as written produces a medium-hot salsa. Use more hot peppers and fewer mild peppers for a fierier salsa. Some examples of mild peppers include bell, banana, and Anaheim. Hot peppers include habanero, jalapeño, and Serrano. Do not change the total amount of peppers or the recipe may not be safe for canning.