Melt the butter in a skillet and add the onions and garlic. Cook, stirring, until onions wilt. Add the meat, salt, pepper, chili powder, and cumin seeds. Break up the meat with the edge of a long-handled kitchen spoon. Cook for 10 minutes.
Add the tomatoes and sugar. Simmer, covered, for 20 minutes more.
Add the beans, cover again, and simmer until beans are thoroughly hot-in about 5 minutes. Serve with a crisp green salad and French or Italian bread.