Cook macaroni in boiling water until tender.
Drain; rinse in cold water.
Melt butter or margarine in skillet, and saute onion and green pepper until soft.
Remove from pan, and combine with tomatoes, cheese and seasonings.
Stir in egg.
Pour over macaroni in greased casserole, and sprinkle with topping.
Bake at 350 Â°F. 30 minutes.