POUND each pork chop with meat mallet, rolling pin or side of a can to 1/4-inch thickness. Place chops in large resealable plastic bag. Add 1/4 cup of the dressing; seal bag. Turn bag gently to coat chops evenly with dressing. Refrigerate 30 min. to 1 hour to marinate. Remove chops from marinade; discard bag and marinade.
PREHEAT oven to 400°F. Coat chops with coating mix as directed on package; discard any remaining coating mix. Place chops in 15x10x1-inch baking pan.
BAKE 20 to 25 min. or until cooked through (160°F). Toss arugula with remaining 1/4 cup dressing; arrange on serving platter. Top with chops; sprinkle with tomato and onion. Serve with lemon wedges.