1 beef top sirloin steak (1 inch thick and 1-1/2 pounds)
3/4 teaspoon salt
1/2 teaspoon pepper
Preheat broiler. In a large broil-safe skillet, heat 1 tablespoon butter over medium heat; saute onion until tender. Transfer to a bowl; stir in cheese and bread crumbs.
Cut steak into 4 pieces; sprinkle with salt and pepper. In same pan, heat remaining butter over medium heat; cook steaks until desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°), 4-5 minutes per side.
Spread onion mixture over steaks. Broil 4-6 in. from heat until lightly browned, 2-3 minutes.