1. Stir the soup, sour cream, salsa and chili powder in a bowl. Stir 1 cup salsa mixture, chicken or beef and cheese in a large bowl.
2. Divide the chicken or beef mixture among the tortillas. Roll up the tortillas and place them seam-side up in a 9"x13" shallow baking dish. Pour the remaining salsa mixture over the filled tortillas. Cover the baking dish.
3. Bake at 350°F for 40 minutes or until the enchiladas are hot and bubbling. Top with the tomato and onion.