Heat oil in 12-inch skillet until hot. Cook chicken over medium heat until brown on all sides, about 15 minutes; remove chicken. Cook and stir onions in oil until onions are tender; drain fat from skillet. stir water, paprika, bouillon cube (dry), pepper and tomato into skillet; loosen brown particles from bottom of skillet. Add chicken. Heat to boiling; reduce heat. Cover and simmer for 20 minutes. Add green pepper; cover and cook until thickest pieces of chicken are done, 10 to 15 minutes longer. Remove chicken; keep warm. Skim fat from skillet. Stir sour cream into liquid skillet. Heat just until hot. Serve with chicken. ( 6 servings.) Bread or rolls are the very traditional accompaniment for this dish.