In small bowl, mix refried beans, onions, chili powder, salt, garlic powder and cumin. In 9-inch microwavable pie pan, spread mixture evenly.
Microwave on High 1 1/2 to 2 1/2 minutes or until thoroughly heated. Sprinkle with cheese. Microwave on High 1 minute longer or until cheese is melted.
Sprinkle tomatoes and lettuce over top. Serve immediately with chips.