If you've ever had Steak au Poivre, this is going to look pretty similar, except it's grilled and there is no pan sauce.
¼ cup peppercorns, cracked
Salt
¾ tsp cayenne pepper
1½ tbsp smoked paprika
1 ea. (1 pound) flank steak
Dijon mustard
Combine the peppercorns, salt, cayenne, and paprika. Set aside.
Brush steak with mustard. Apply seasoning mixture and gently massage into meat.
Grill over high heat until marked on both sides. Lower heat to medium and cook, turning often, until internal temperature reaches 140 °F for medium rare.
Remove and let rest, uncovered, for 7 minutes.
7 minutes
Slice as thinly as humanly possible across the grain and serve warm.