MICROWAVE: In a 2 quart (2 L) microwaveable covered casserole, melt margarine on LOW for 30 seconds. Add onion. Cook on HIGH 1-2 minutes UNTIL ONIONS ARE SOFT. Add tomatoes. Cover and cook on HIGH for 5-7 minutes until tomatoes boil. Beak eggs over tomatoes. Pierce yolks. Cover and cook on HIGH 3-5 minutes until eggs are desired doneness. Remove cover. Sprinkle with cheese. Cook on HIGH 1 minute to melt cheese.