Heat the grill over high heat. Whisk together the cumin, sea salt, and black pepper in a small bowl, and sprinkle over the steak. Use clean hands to rub the seasoning into the steak.
Once the grill is smoking, place the steak on top and grill for 4 minutes; flip and grill an additional 4 minutes. Allow the steak to rest on a cutting board for 5 minutes.
While the steak rests, combine the ingredients for the chimichurri sauce in a food processor. Pulse until well combined.
Slice the steak, and spoon the chimichurri sauce over the top.