Wrap a baking sheet with aluminum foil, and place a cooling rack on top of the baking sheet. Generously salt and pepper the steak, and place the steak on top of the cooling rack. Let it sit uncovered on the counter for an hour, or place it in the fridge uncovered overnight. (If you refrigerate the steak, let it come to room temperature for one hour before cooking).
Preheat oven to 200°F. Place the steak in the oven, and cook until a thermometer inserted into the thickest part of the steak registers 105-110°F for medium-rare (120°F for medium-well), about 30-45 minutes. I start checking for doneness at 30 minutes. Once it reaches your desired temperature, the steak can sit on the counter for up to two hours before you finish cooking.
Heat a cast-iron skillet (or another large non-stick skillet) over medium-high heat. Add the butter and oil, and stir to coat the bottom of the pan. When it starts to smoke, place the steak in the skillet and cook 1-2 minutes per side until it's very browned and develops a nice crust. Transfer the steak to a cutting board, and let it rest for 10 minutes. Slice the steak against the grain.