1. Cook corn according to package instructions. Preheat oven to 375 degrees F. Brown beef and onions with taco seasoning and garlic powder. Add refried beans to the cooked beef. Stir until well mixed. Heat on medium heat for about 5 minutes.
2. Place 3 tortillas on the bottom of a 13x9 pan sprayed with cooking spray to create a single layer of tortillas. Spread ½ of the beef/bean mixture evenly on the tortillas. Spread ½ of the salsa evenly over the beef/beans. Sprinkle 1 cup of cheese evenly over salsa. Spread ½ cup of corn evenly over the salsa. Spread ¼ cup of tomatoes over corn. Repeat layers once.
3. Bake for 30 minutes or until salsa bubbles for a couple of minutes. Serve with shredded lettuce, sour cream, and salsa.