Roast-Beef Cheddar Panini

From Southern Living.

• Ready In: 16 mins
• Serves: 4

Ingredients

• 1  large onion, sliced
• 1  teaspoon sugar
• 1⁄2 teaspoon salt
• 1⁄2 cup  prepared creamy  horseradish sauce, divided
• 8  slices  whole wheat bread
• 1  lb deli roast beef, slices
• 4  slices cheddar cheese (or Swiss cheese, or provolone cheese)
• 1  tablespoon  melted butter

Directions

1. Stir/saute the first 3 ingredients in a lightly greased skillet over med-high heat for 8 minutes or until the onion is tender.
2. Spread 1 T. horseradish sauce on each of 4 bread slices; top evenly with roast beef, cooked onion, and cheese.
3. Top with remaining bread slices.
4. Brush melted butter on both sides of sandwich.
5. Cook in a preheated panini press 2 to 3 minutes or until golden brown.
6. Serve with remaining horseradish sauce.