Season the steak on both sides with the salt and place on a rack set inside a sheet pan for about 10 minutes at room temperature while you heat your oven.
Heat the oven to 200°F.
Insert a probe thermometer horizontally through the side of the steak and roast the steak until it reaches an internal temperature of 120°F, about 30 minutes. Remove the steak from the oven and rest uncovered for 10 minutes.
Meanwhile, place a 12-inch cast iron skillet over high heat until it reaches at least 600°F, about 10 minutes. (You'll know you're close when a half teaspoon water dropped into the middle of the pan is completely evaporated in 5 seconds).
Brush a very light coat of peanut oil onto both sides of the steak. Sear steak on each side for 1 minute.
Rest the steak on a rack 5 minutes, and then slice diagonally against the grain to serve.