For speed, start with canned beans. To cook your own dried beans, start with 2 pounds. If making up to 2 days ahead, cover and chill. Reheat in a microwave oven or stir occasionally over medium heat.
1. In a 5- to 6-quart pan over medium-high heat, combine tomatoes, onion, chilies, and garlic. Stir often until onion is slightly browned, about 10 minutes.
2. Add beans. Cover and simmer, stirring occasionally, until hot, about 10 minutes. Season to taste with salt and pepper. Pour into a bowl.