Combine salt, pepper, cayenne, rosemary, and smoke powder. Set aside.
Brush steak liberally with Dijon mustard. Apply seasoning mixture and gently rub into meat. Refrigerate for at least 1 hour.
Heat a charcoal grill with a chimney starter (not that solvent stuff). Reapply the grate and place the steak on top. Cook, flipping once, until internal temperature reaches 145°F for medium rare.
Remove and let rest for 10 minutes. Slice as thinly as humanly possible across the grain. Serve warm.