Combine marinade ingredients in a saucepan.

Simmer 5-10 minutes.

Let cool to room temperature.

Rub flank steak with garlic powder and tenderizer mixture.

Pour room temperature marinade over steak, and marinate for at least 8 hours.

Grill over high heat, 8 minutes on the first side, 7 minutes on the second. Remove from grill.

Slice across the grain on a slight angle.