Rub sirloin steak with sea salt, pressing until salt sticks on both sides and steak is evenly coated.
Preheat grill for medium heat and lightly oil the grate.
Cook steak on the preheated grill until browned, about 5 minutes. Flip steak; scrape as much salt off the top as possible. Continue cooking until second side is browned and center reaches desired doneness, 5 to 10 minutes more. Scrape salt off the second side and serve.