Process roasted cacao nibs in a food processor until finely ground. Season steaks with kosher salt and pepper. Rub ground cacao nibs on both sides of steaks (about 1 1/2 tsp. each). Let steaks stand at room temperature 30 minutes.
Preheat grill to 300° to 350° (medium) heat. Grill steaks, covered with grill lid, 5 to 7 minutes on each side or to desired degree of doneness. Let stand, loosely covered with aluminum foil, 10 minutes. Serve with Béarnaise Butter and Onion Relish.
Note: We tested with Taza Chocolate Organic Roasted Cacao Nibs.