If steak is chilled from a refrigerator, leave it on your kitchen counter, covered, until it returns to room temperature, up to an hour.
Pat steak as dry as possible with paper towels
When the steak is ready, pre-heat your oven to 400 degrees.
While it is preheating, heat a 12-inch or larger cast iron pan on high heat on a burner. Let it heat up for 10-15 minutes, until it is very hot.
Meanwhile, very generously salt and pepper the steak on both sides. The salt and pepper help with the steak's crust, so don't be shy.
When the pan is very hot, carefully place the steak on the pan. It may smoke, so make sure you have adequate ventilation. Cook 4 minutes, undisturbed, and then carefully flip to the other side and cook for 4 minutes more.
Transfer the pan to the oven and cook for 8-12 minutes until desired internal temperature. If you have a meat thermometer, use it! (130 degrees for medium rare).
Remove from oven and immediate remove steak to a plate or cutting board. Allow it to rest for 10 minutes, then thickly slice against the grain. Top with some of the pan drippings.