Allow steak to come to room temp. Preheat grill to medium high. Preheat oven to 300 degrees. Generously rub steak with oil, kosher salt and pepper on all sides. Grill steaks approx. 2 min per side, until marked. Transfer to oven-proof pan and pour melted butter over steak. Finish cooking steak in oven, or covered grill set to low heat, basting with pan juices 2-3 times, approx. 20 min or until internal temp reaches 120 degrees for medium rare. Let rest 10 min before slicing (temp will continue to rise 5-10 degrees as steak rests). Because of the thickness of this steak and the presence of the bone, a probe thermometer is highly recommended. Slice steak off bone in thin slices, against the grain. Top with flake sea salt and basil, and serve warm.
Chef's note: Restaurants often use this method of marking on a hot grill and finishing in an oven for thick cuts of steak, fish, poultry and pork to achieve a juicy interior and to avoid a dark, overdone exterior.