Sauté onions and green peppers in skillet until heated thoroughly. Add cooked rice, drained black beans, and tomato sauce and cook for an additional 5 minutes. Remove from heat and stir in ½ cup of cheese. Spoon mixture into pepper halves and then place in 9 x 13 glass baking dish. Pour hot water in the bottom of the dish and cover with aluminum foil.
Bake for 30 minutes; sprinkle with remaining cheese and bake uncovered for an additional 10 minutes.