Trim steak. Cut in serving portions. Marinate in 2 tablespoons olive or salad oil, 2 tablespoons lemon juice and 2 tablespoons catsup. Let stand at least 30 minutes, turning once or twice. Sprinkle steaks with Worcestershire sauce, onion and 2 tablespoons butter. Bake at 400° for 15 minutes. Reduce heat, bake until tender. Cover part time to keep moist. Add mushrooms, if desired.