First, get some nice, healthy tomatoes. Rinse well in cold water.
Keep in mind that what you start with will decrease almost 50% in volume by the end of the process, so make how much you think you will use. I used about 20 large tomatoes and got four pints out of it. :-)
Peel the tomatoes using which ever method you prefer. Some prefer to blanch and peel, I simply used a paring knife.
Chop the peeled tomatoes and put them in a stock pot.
Then, either blend them with a stick blender, or otherwise mash them. I used my handy dandy, old-fashioned potato masher. :-)
When they are mashed well, set them to simmer, uncovered, on medium-low for 2-3 hours, or until desired consistency is reached, stirring often to prevent burning. Again, volume will likely be reduced by half.
When you've reached that consistency that you like, ladle into prepared jars leaving 1 inch of head space and hand tighten the lids on.
Pressure can for 15 minutes for pints, or 20 minutes for quarts, referencing the following altitude charts. Tomato sauce can be water bath canned if lemon juice is added, just add 1 Tablespoon of lemon juice per pint of tomato sauce, or 2 Tablespoons of lemon juice per quart.
See Simply Canning for more info as well.
