Rinse beans; drain well and set aside.
Saute onion, green pepper, and garlic in olive oil in a Dutch oven until vegetables are tender. Add beans, stewed tomatoes, water, tomato sauce, vinegar, sugar, pepper, and salt; bring mixture to a boil. Cover, reduce heat, and simmer 1 hour. Uncover and simmer an additional 20 to 30 minutes, stirring occasionally.
Serve black beans over hot cooked yellow rice. Top each serving with chopped green onions and a dollop of sour cream. Yield: 6 to 8 servings.