HEAT oven to 425°F. CRUMPLE 4 large sheets of foil to make 4 (3-inch) balls; place on baking sheet. Place 1 tortilla over each ball; spray with cooking spray. Bake 6 to 8 min. or until tortillas are golden brown. (Tortillas will drape over balls to form shells as they bake.) MEANWHILE, cook meat with taco seasoning mix as directed on package. FILL shells with lettuce, meat mixture, cheese and tomatoes just before serving. Drizzle with dressing.