This recipe is brought to us by Lee Hanson and Riad Nasr, chefs at New York City's Balthazar and Pastis restaurants.
Preheat oven to 450 degrees. Place a large cast-iron skillet in oven to heat. Season beef generously with salt and pepper.
Remove the skillet from the oven, and place over medium-high heat. Add the beef and sear until brown, about 3 minutes per side.
Transfer to oven, and cook for 15 minutes. Turn, and cook 10 to 15 minutes more for medium-rare; an instant-read thermometer should read 130 degrees.
Remove from oven, and let stand for 10 minutes. Carve, and serve drizzled with sauce. Serve with onion rings on the side.