Preheat overn to 250 degrees
Pat steaks dry with paper towels
Liberally salt and pepper both sides of a stake, placing them on a baking rack in a rimmed sheet pan.
(Optional) Put steaks in the fridge (on the pan/rack) for serveral hours or ovvernight.
Insert meat thermometer, then move steaks into the overn.
At 15 degress before the overn-target temp, pot the cast iron skillet on the highest setting of the strongest burner.
At the oven-target temp, add oil to the skillet then add the steaks from the oven.
Add butter, slightly tilitng the skillet to baste the steak for 45 secods to one minute on each side. Then use tongs to hold the stakes vertically to brown the sides.