1/2 c. chopped onion
2 tbsp. butter
1 lb. Velveeta Mexican cheese (mild or hot)
1 (16 oz.) can tomatoes, chopped

Microwave onions in butter in 1 1/2 quart casserole on high for 2 minutes or until onions are tender. Add remaining ingredients, mix well. Microwave on medium 9 minutes or until thoroughly heated. Stir every 3 minutes. Serve hot with tortilla chips.