Set a large cast iron pan or griddle over high heat and let this heat up for 1-2 minutes. Add the tablespoon of oil to the pan and let this heat up for 1 minute. Add the steak, frying on each side for 3 minutes, or to desired doneness (3 minutes per side
will yield approximately medium rare doneness for an average cut of flank steak; Carne asada and skirt steak will need less time). If the pan starts to smoke too much, reduce the heat to medium-high. You want the steak browned, not burned. Remove from pan and let sit, tented with foil, for 5 minutes.