Preparation Make the pickled onions: Squeeze the lime juice into a bowl and add the onion or shallot, a large pinch of salt and a small pinch of sugar. Let rest for 20 minutes while you make the chili. Heat a large skillet, then add the oil. When hot, add the onion and sauté until softened. Add the garlic, chile powder and oregano and sauté until fragrant. Add the beans and tomatoes and a few large pinches of salt and let simmer until the tomatoes break down, about 20 minutes. Taste and add more salt, chile and/or oregano to taste. Serve with the pickled onion and any of the garnishes you like.