About 1 hour before grilling, take the steaks out of the refrigerator and place them on a plate or tray at room temperature.
Place butter in a small bowl and soften slightly if needed, then rub butter over both sides of each steak (about 1 tablespoon per side).
Season both sides of each steak with the Montreal steak seasoning and the Chef Paul blackened steak seasoning, using as much as you prefer to coat the surface.
Let the seasoned steaks rest on the counter for about 1 hour to come closer to room temperature.
Preheat your grill on high heat until very hot.
Place the steaks on the hot grill and expect occasional flare-ups from the butter; when flames occur, reduce the heat to medium to control charring.
Grill the steaks about 5 minutes on the first side, until dark brown with clear grill marks, then flip and grill about 5 minutes more on the second side.
Check doneness with an instant-read thermometer or by touch: rare 120°F, medium-rare 130°F, medium 140°F, medium-well 150°F, well 160°F.
Remove the steaks from the grill and let rest at least 5 minutes before cutting, as internal temperature will rise slightly while resting.
Serve sliced or whole as desired.