Preheat oven to 375 degrees with rack in center position.
Pat steak dry thoroughly with paper towels.
In a spice grinder, combine cumin, coriander, and peppercorns. Pulse until coarsely ground and transfer to a medium bowl. Add salt, paprika, brown sugar, oregano, and garlic and mix until combined.
Rub steak on all sides with spice mixture and let stand at room temperature for 3 to 4 hours or up to overnight in the refrigerator. If marinating in refrigerator, remove 1 hour before cooking to bring steak to room temperature.
Heat a large cast-iron pan over medium-high heat. Sear steak on both sides until blackened, 8 to 10 minutes total. Transfer to oven and roast 15 to 20 minutes or until a meat thermometer inserted into center of steak registers 125 degrees for medium-rare.
Transfer steak to a carving board and let stand at least 15 minutes before slicing and serving.