The flap steak has unique muscle fibers that have an amazing texture. The meat comes from the belly of the cattle, and the workout they get from living a pasture-raised lifestyle intensifies the deep flavors of this cut of beef.
This cut is truly amazing when seasoned with lots of salt, grilled over high heat, then served with chimichurri. It also holds a marinade really well, just make sure you clean it off before cooking over high heat, or the marinade will burn. Finally, take special care to cut against the grain.