In large skillet, cook hamburger, onion until meat is no longer pink. Drain. Stir in salsa, beans, dressing, taco seasoning, cumin. Place three tortillas in 2-qt. baking dish coated with cooking spray. Layer with half of meat mixture, sour cream (opt.) and cheese. Repeat layers.
Cover and bake at 400 degrees for 25 min. Uncover; bake 5-10 min. longer or until heated through. Let stand 5 min before serving. Top with lettuce, tomato and cilantro if you want to pretty it up.