Lay flank steak on cutting board and with a filet knife cut a pocket (most difficult part) in the steak. Inside the pocket put grilled onions, dried basil and provolone cheese. Close the pocket with a skewer. Season the outside with your favorite BBQ rub or just salt & pepper. Grill on medium high until steak is no more cooked than medium - medium rare. Remove from grill and allow to rest 10 minutes. Slice across the grain and top with your favorite spaghetti sauce and serve with pasta as a side dish.