Flat-iron steak is on sale at my grocery store. How should I cook it?
As ChefOno noted hanger steak is great on the grill especially over a real wood charcoal fire. Shamless plug, go to "Features" and select "Not recipes" and you will see my tips on grilling steak. For hanger steak I would think about cooking to an internal temperature not much over 120F. And for God's sake don't flip it.