(recipe, Rose Levy Beranbaum)
I prefer to leave this sauce chunky, but for a smooth sauce, simply process it for a few seconds in a food processor.
Culinate editor's note: You can use fresh tomatoes in place of the canned or cooked tomatoes. You'll just need to simmer the sauce a good deal longer (about half an hour), and you may want to pick out the shriveled tomato skins when the sauce is done. Puréeing the sauce a bit with an immersion blender gives the sauce a smoother texture.