Marinade
Butter
Zest, then juice the lemon and set aside the zest to use in the butter. In a medium bowl whisk the marinade ingredients, including 2 tablespoons of the lemon juice (save any extra juice for another use). Place the steak in a large, resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade, place on a plate, and refrigerate for 2 to 4 hours, turning occasionally. Allow the steak to stand at room temperature for 20 to 30 minutes before grilling.
Prepare the grill for direct cooking over medium heat (350° to 450°F).
In a medium bowl mash the butter ingredients with the back of a fork and mix well to distribute the seasonings evenly.
Remove the steak from the bag and discard the marinade. Brush the cooking grates clean. Grill the steak over direct medium heat, with the lid closed as much as possible, until cooked to your cooked to your desired doneness, 8 to 10 minutes for medium rare, turning once or twice (if flare-ups occur, move the steak temporarily over indirect heat). Remove from the grill and let rest for 3 to 5 minutes. Smear the butter over the top. Cut the steak across the grain into thin slices. Serve warm.