Wash tomatoes, remove any bad spots and core. Slice into quarters.
Put about a pound of tomato slices into stockpot over medium-high heat. Heat to boiling while crushing tomatoes. Continue to add tomato quarters a few at a time, while maintaining the boil. Continue to crush and stir tomatoes as they cook. This will help keep sauce from separating after canning (not a big deal if it does, just stir it in, but it does look prettier!). After the last tomatoes are added to the boiling mixture, crush, and simmer for another 5 minutes.
Put cooked tomato mixture through a food mill or sieve to remove peels and seeds leaving just the pulp.
Put tomato pulp back into stockpot with basil, sugar, oregano, salt, garlic powder, black pepper and red pepper flakes. Simmer until desired consistency is reached, stirring often. OR put as much of the puree into a large slow cooker with the spices. Leave the lid off and turn on HIGH. Allow to cook down, adding more of the tomato pulp as you have room. Continue to cook down in the uncovered slow cooker until it is the thickness you like. I reduce the volume by about one-half for a thicker sauce.
In well cleaned, hot pint jars, put 1 tablespoon bottled lemon juice in each jar. Ladle hot pizza sauce into jars, leaving a 1/4" headspace. Wipe jar rim with a damp cloth, put on lid and put on jar band finger tip tight.
Using a boiling water bath method, process jars for 35 minutes at 0-1,000 ft altitude, 40 minutes for 1,001 - 3,000 ft, 45 minutes for 3,001 - 6,000 ft and 50 minutes for above 6,000 feet altitude.
To freeze: Allow finished sauce to cool. You do not need to add lemon juice if you are freezing sauce. Taste and adjust seasonings as needed. Package one pint worth of sauce into freezer safe containers with 1/2" head space. Seal, label and freeze.