Heat the oil in a sauce pan. Saute the onions until brown and caramelized. Add the garlic and cook until the garlic is golden brown. Add the beans and spices and cook until hot. Remove from heat, and mash with a potato masher or process in a food processor until smooth. If the beans are too thick, you can thin them out with a little bit of picante sauce.
Serve with your favorite Mexican dish. If you want to make a bean dip, only drain one can of the black beans and add the liquid from the other can to the pot. Pinto beans will also work instead of the black beans.