"Mix yogurt, salt, pepper and garlic in bowl.Mix meat with yogurt and marinate 1 to 2 hours at room temperature, up to 2 days refrigerated.Thread meat on skewers and grill over barbecue.Place bread on plates (if using tortillas, toast briefly over flame), divide meat among them, top with tomato, onion slices and cilantro and fold bread over.Serve with lemon or lime quarters for squeezing."