Flat Iron Steaks with Balsamic Baked Vidalia Onions

Ingredients:

2 tablespoons butter
1 cup balsamic vinegar
1 tablespoon chopped rosemary
1 teaspoon kosher salt
½ teaspoon freshly ground black pepper
2 Vidalia onions, quartered
1 Flatiron steak (about 1 ¼ pounds)
Kosher salt
Freshly ground black pepper
2 teaspoons canola oil

Instructions: 

1.  Preheat oven to 400º.
2. Melt the butter in a small saucepan, add the balsamic vinegar, rosemary, salt and pepper and bring to a boil.
3. Pour into a buttered 2 quart ovenproof casserole dish. Add the quartered Vidalia onions. Toss to coat and bake 40 minutes, turning and basting twice during cooking.
4. Season steak generously with salt and pepper. Heat 12” cast iron skillet over high heat. Add canola oil and swirl to coat bottom of pan. Add steak and sear for 4 minutes.
5. Turn steak over and place pan in oven with onions. Cook in oven 5 minutes for rare; 9 minutes for medium.
6. Serve with the Balsamic Baked Vidalia Onions.