Wash the tomatoes really well and cut them into quarters. Remove any stems or bad spots.

Bring a large pot of water to a boil. Quickly place the tomatoes in for about a minute to loosen the skins, then move them into a bowl of ice water to stop the cooking.

Once the tomatoes are cool enough to handle, peel off their skins and scoop out some of the seeds if a smoother paste is desired.

Crush the tomatoes by hand or run them through a food mill or blender until you achieve a nice, even puree.

Pour the puree into a large heavy pot and cook it over medium heat, stirring frequently to prevent sticking or burning.

As the mixture starts to thicken, add in the salt and optional sugar if desired.

Continue simmering until the mixture reduces to a thick paste, which can take some time, so be patient and stir occasionally.

Sterilize your quart jars by boiling them in water. Once clean, add 2 tablespoons of bottled lemon juice to each jar for safe canning.

Ladle the hot tomato paste into the jars over the lemon juice, leaving some space at the top.

Process filled jars in a boiling water canner for about 35 minutes for quart jars to properly seal them.

Let the jars cool completely before storing them in your pantry.