Blend tomatoes, barbecue sauce, half each of the onions and cilantro, and 2 chiles in blender until smooth; pour 2 cups into 13x9-inch baking dish. Set remaining sauce aside. Chop remaining onion.
Prepare Dinner as directed on package. Stir in 4 Singles until melted. Meanwhile, brown meat with chopped onions in large skillet; drain. Stir meat mixture and remaining cilantro into prepared Dinner; spoon into remaining chiles. Place filled chiles over sauce in baking dish; top with remaining sauce. Cover.
Bake 25 min. or until heated through. Cut remaining Singles in half; place over chiles. Bake, uncovered, 2 min. or until melted.