Heat a grill, grill pan, or broiler.
Combine all ingredients except steak in a large bowl. Season steak with salt and pepper and then add to marinade. Marinate for 40 minutes. Thread steak onto skewers* and then grill or broil, turning occasionally, until cooked to desired degree of doneness. Transfer to a serving plate and sprinkle with green onions and cayenne pepper, if desired.
*Cook's Note: If using wooden skewers, soak them in water for at least 10 minutes before threading meat.