Ingredients
2/3 cup balsamic vinegar
1 tablespoon olive oil
6 cups vertically sliced onion (about 1 1/2 pounds)
1/2 teaspoon salt, divided
1 (1-pound) flank steak, trimmed
1/4 teaspoon freshly ground black pepper
1/4 teaspoon dried thyme
Bring balsamic vinegar to a boil in a small, heavy saucepan. Reduce heat to medium; cook until reduced to 1/4 cup (about 5 minutes). Remove from heat.
Heat oil in a large nonstick skillet over medium-high heat. Add onion, and sauté 10 minutes or until tender. Sprinkle with 1/4 teaspoon salt; sauté 18 minutes or until onions are golden brown. Remove from heat.
Preheat broiler.

Sprinkle steak with remaining 1/4 teaspoon salt, pepper, and thyme. Place steak on a broiler pan coated with cooking spray; broil 6 minutes on each side or until desired degree of doneness. Cut steak diagonally across grain into thin slices. Serve steak over
Onions and drizzle 25 Star Balsamic.

Really easy recipe, and so delish.