Bring a large Dutch oven or stock pot of water to a boil over high heat. Fill a mixing bowl with ice and water and set next to stove.

Core the stems from the tomatoes and slice a shallow “X” in the bottom of each fruit

Working in batches, drop several tomatoes into the boiling water. Cook until the skin starts to wrinkle and split – 45 to 60 minutes. Lift the tomatoes out with a slotted spoon and plunge into ice water. Continue with the rest of the tomatoes, transferring the cooled tomatoes from the ice water to another mixing bowl as they cool. Discard the boiled water when finished.

When finished blanching, use a paring knife to strip the skins from the tomatoes.

Working in batches, pulse the tomatoes in the food processor. Pulse a few times for chunkier sauce, or process until smooth for a pureed sauce. Transfer each batch into the Dutch oven. 

Bring the tomato sauce to a simmer over medium heat. Continue simmering for 30 to 90 minutes stirring occasionally until the sauce reaches the taste and consistency you like.

Stir in the lemon juice or vinegar and salt. A quarter cup is the minimum needed to ensure a safe level of acidity for canning, however you can add more to taste.

Let the sauce cool, then transfer into freezer containers/bags. Sauce can be kept frozen for at least 3 months.

Alternatively, transfer the sauce into sterilized canning jars. Top with new, sterilized lids and screw on the rings until finger tight. Process in a pot of boiling water for 30 minutes. Let cool completely on the counter – if any lids do not seal completely refrigerate that sauce and use it within a week, or freeze up to three months. Canned tomato sauce can be store in a pantry for up to one year.