Sprinkle both sides of the steak with salt.
In a large skillet, preheated over high heat, pan-broil the steaks, until the large ones are almost done to taste, or the small ones are well browned. If using large steaks, you probably will not be able to fit them all in the pan at once. Do a couple at a time, then remove them and set them aside while cooking the rest. The small steaks should fit comfortably in the pan side by side, but if they crowd the pan, do not brown them all at once. When all the steaks have been cooked, pour off any fat in the skillet.
Add the 2 cups of tomato sauce and dried oregano to the pan, scraping up any brown film or bits in the pan. Return the cubed steaks to the pan if you are using them and they were set aside. Bring to a simmer over high heat. If using cubed steaks, cover the pan and adjust the heat so the tomatoes simmer gently for about 40 minutes, or until the meat is tender.
Place each steak on dinner plate and top with sauce. If the sauce on the cubed steaks is not thick enough, uncover pan at the end of the cooking time and reduce.
In a 1 1/2- to 2-quart saucepan, combine the oil and onion and cook over medium heat, stirring frequently, until the onion is fully tender and golden, 8 to 10 minutes. Or, over medium-low heat, combine the oil and the garlic. Cook the garlic, pressing it into the oil a couple of times to release its flavor, until it barely begins to color on both sides. Remove the garlic.
With a food mill, puree the tomatoes directly into the pot and stir well. Add salt and either hot pepper flakes or black pepper to taste. Increase the heat slightly and bring to a brisk simmer. Adjusting the heat as the sauce cooks down, and stirring frequently, simmer briskly for about 12 minutes, until the sauce has thickened and reduced.
Season with herbs according to the recipe you are preparing. For the most basic sauce, add a few torn basil leaves or a tablespoon of finely cut parsley while the sauce is simmering. Then add a little more at the end of cooking.