In a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in the salsa, beans, dressing, taco seasoning and cumin. Place 3 tortillas in an 11x7-in. baking dish coated with cooking spray. Layer with half of the meat mixture, sour cream and cheese. Repeat layers., Cover and bake at 400° for 25 minutes. Uncover; bake until heated through, 5-10 minutes longer. Let stand for 5 minutes; top with lettuce, tomato and cilantro.