Add all ingredients to a blender and blend until very smooth, it should be fairly thin.
Heat 2 TB oil in a large skillet(no teflon) over high heat until very hot, but not smoking. Add the contents of the blender to the skillet and "fry" the sauce, stirring constantly, and scraping the bottom of the skillet to keep from sticking. Be careful, it makes a mess in the kitchen, but it is well worth it, be sure to wear your apron! Fry the sauce for 10-15 minutes, until it is reduced and the flavors have blended well. Keep warm and use immediately, or store it in the fridge for 2 days, or in the freezer for two months. If using frozen, allow to thaw first and reblend quickly as it tends to separate.
* Cut the tomatoes in half and grate them with your cheese grater right down to the skin. This retains the pulp, and not the skin, without having to boil them. Discard skins. You can used canned tomatoes too if you don't have time.
* Use chipotles for a nice smoky flavor.
* Amount of chiles given makes a picante dish. Omit if you don't like it spicy, but I recommend at least one to give it some flair.