Grill Pan Method:
To use a grill pan or cast iron skillet: Preheat dry grill pan or 12-inch cast iron skillet directly over medium heat. With a heat resistant brush, carefully brush a small amount of oil on the hot grill pan or skillet. Season steak with kosher salt. Place meat in pan or skillet and sear 2 minutes; cover grill and grill for 3 minutes. Uncover grill; turn steak with a pair of tongs and sear second side for 2 minutes. Replace lid; continue grilling about 5 minutes or more till desired doneness (160 degree F for medium doneness). Uncover grill; continue grilling for 1 minute more or till liquid (steam) evaporates.
Flank steak should be served medium rare and cut across the grain for maximum tenderness. This recipe can be served on small slices of baguette for a substantial cocktail party appetizer, on hearty whole-grain bread for a Dagwood sandwich or sliced and drizzled with the Chimichurri sauce and roasted new potatoes for a main course.