Get a meat thermometer you can use in the oven. Preheat the oven to 375, and put a pan on the stove on medium high. Let the steak rest on the counter for a few minutes, pat dry, and lightly coat it in olive oil, salt, and pepper. Sear for two minutes each side, then put the pan in the oven with a slice of butter on the steak. Cook about 5 minutes each side, using the meat thermometer to remove the steak at 120 degrees, or 125 for more medium than rare. Put the steak aside, lightly tented with foil to rest for another few minutes. Eat.
If the steak has a big strip of fat, make cuts along the fat, pointing the knife towards the steak, and it won't curl up. Make sure you sear the fuck out of that fat strip while you sear the rest of the steak.