- 2tablespoons butter
- 1cup balsamic vinegar
- 1tablespoon chopped rosemary
- 1teaspoon kosher salt
- 1/2teaspoon freshly ground black pepper
- 2 Vidalia onions, quartered
- 1 flatiron steak (about 1 1/4 pounds)
- Kosher salt
- Freshly ground black pepper
- 2teaspoons canola oil
- Preheat oven to 400F.
- Melt the butter in a small saucepan, add the balsamic vinegar, rosemary, salt and pepper and bring to a boil. Pour into a buttered 2-quart ovenproof casserole. Add the quartered Vidalia onions. Toss to coat and bake 40 minutes, turning and basting twice during cooking.
- Season steak generously with salt and pepper. Heat a 12-inch cast-iron skillet over high heat. Add canola oil and swirl to coat bottom of pan. Add steak and sear for 4 minutes. Turn steak over and place skillet in oven with onions. Cook 5 minutes for rare (9 minutes total cooking time).
For more information on why meat needs to rest after cooking, watch this video for tips from the “Butcher Boys” of Porter Road Butcher in Nashville, TN