Flank steak comes from the belly of the cow. It has almost no fat should be grilled hot and fast to medium rare, between 130 and 135 degrees as measured with a digital thermometer in the thickest part of the steak. You can see the long strands in the photo, heading from east to west. To make tender slices, you’ll need to cut the meat across the grain, meaning from north to south. Make the slices as thin as possible for maximum tenderness. A marinade will also add flavor, but not significantly more tender.