HEAT large nonstick skillet sprayed with cooking spray on medium heat. Add steak; sprinkle with pepper. Cook steak 5 to 6 min. on each side or until medium doneness (160ºF). Remove from skillet, reserving drippings in skillet. Place steak on cutting board; cover loosely with foil.
ADD onions and garlic to skillet. Stir in dressing; cover with lid. Cook 5 min.; stir. Cook, uncovered, an additional 4 to 5 min. or until onions are tender, stirring occasionally. Meanwhile, cut steak across the grain into thin slices; place on serving platter.
TOP steak with the onion mixture; sprinkle with cheese. Serve with the broccoli.