Ingredient:

• 10 thin slices sweet onion
• 2 tablespoons butter, softened, divided
• 1/2 pound lean ground beef (90% lean)
• 1/4 teaspoon salt
• 1/4 teaspoon pepper
• 4 slices rye bread
• 2 tablespoons Thousand Island salad dressing
• 2 teaspoons prepared horseradish
• 2 slices process American cheese or Swiss cheese