Serves 6 to 8

(If using dried beans, wash and rinse well, discarding broken and deformed beans. Place in pot with enough water to cover, plus 2 inches; soak for 8 hours or overnight. Drain, rinse and return to pot. Add water and cook 45 minutes to an hour.)

Heat oil in heavy large saucepan over medium heat. Add onion, bell pepper, garlic, serrano pepper, and cumin and saute until vegetables begin to soften, about 5 minutes. Add 1 cup of beans to pan. Using back of fork, mash beans coursely. Add remaining beans, broth, lime juice, cilantro and vinegar and simmer until mixture thickens and flavors blend, stirring occasionally, about 15 minutes (3 - 5 hours, if using dried beans.) Mix in sugar and season beans to taste with salt and pepper. Serve with white rice.