Flank Steak with Red Onion Marmalade

Ingredients
3 tablespoons butter
2 medium red onions, thinly sliced
3 tablespoons distilled white vinegar
3 tablespoons sugar
1 teaspoon salt
1 beef flank steak (1 1/2 pounds)
1/4 teaspoon coarsely ground pepper

Directions

1. In nonstick 12-inch skillet, melt 2 tablespoons butter over medium heat.
2. Add onions and cook, stirring occasionally, until tender, about 15 minutes.
3. Stir in vinegar, sugar, and 1/2 teaspoon salt.
4. Reduce heat and simmer 5 minutes.
5. Spoon red onion marmalade into small bowl; keep warm.
6. Wash skillet and wipe dry.
7. Sprinkle steak with pepper and remaining 1/2 teaspoon salt.
8. In skillet over medium-high heat, melt remaining 1 tablespoon butter.
9. Add steak and cook 6 to 8 minutes per side for medium-rare or until desired doneness.
10. Slice steak and serve with red onion marmalade.