Wash and quarter the tomatoes. If desired, you can remove the tough core, but it's not essential for this method.

In a large pot or Dutch oven, combine the quartered tomatoes and fresh lemon juice. If using, add the salt.

Bring the mixture to a boil over medium-high heat, stirring occasionally. Once boiling, reduce the heat to low, cover, and simmer for 20 minutes, stirring occasionally.

Carefully transfer the hot tomato mixture into clean jars, leaving about 1 inch of headspace. You can either pack them whole or pulse them briefly in a food processor for a smoother consistency before jarring.

Process the jars in a boiling water bath according to the manufacturer's instructions for your canner. Typically, this involves processing pint jars for 15 minutes and quart jars for 20 minutes at sea level, adjusting for altitude.

Remove the jars from the canner and let them cool undisturbed on a towel-lined counter for 12-24 hours. Check seals before storing.