Heat oven to 350 degrees F. Grease an 8- to 9-inch square pan.
Melt butter or margarine in skillet. Add onions, stirring until crisp tender.
Stir in chiles. Spoon chile mixture into pan, then sprinkle with cheeses.
In a small bowl, beat eggs slightly. Beat in sour cream and pepper flakes. Spoon
egg mixture over cheeses and sprinkle with tomato or salsa.