What makes this sauce so good is the long, slow cooking time, which allows it to develop a complex flavor. It shouldn't simmer; there should be just a bubble rising to the surface every now and then. Meaty beef bones add more depth and complexity. (If you have beef stock, you can add two cups of it in place of the beef bones.) This sauce is chunky with abundant tomato and sliced garlic. Depending on what you're using this for, it can be served as is (over a very thick hearty pasta or as part of a braising liquid). But if you were to use it for an angel hair or as a sauce for sauteed veal, you would probably want to puree it in a blender until it's uniformly smooth. This sauce freezes well, so you can make big batches, portion it into smaller containers, and freeze it when you need it.
Heat the oil in a 4-quart saucepan or large Dutch oven over medium heat. Add the onions and cook until translucent, 2 minutes. Add the salt and garlic and cook until everything is soft but not browned, about 3 minutes.
Squeeze the tomatoes one by one into the pan, pulverizing them by hand, and pour in their juice, too. Add the bones, wine, oregano, red pepper flakes, if using, black pepper and bay leaf. Bring the sauce to a simmer, and then reduce the heat to its lowest possible setting, and continue to cook for 8 hours. The sauce should reduce by about one-third.
Taste for seasoning and add more salt if necessary. Remove the bones and bay leaf. If not using right away, let the sauce cool, then cover and refrigerate for up to 1 week or freeze for up to 2 months.