Remove steak from the refrigerator 45 minutes before cooking, and salt generously on both sides. Spray a rimmed baking sheet with cooking spray, and preheat the oven to 225 degrees
Sprinkle black pepper on both sides of the steak before placing in the oven on the middle rack. Cook for 30-45 minutes. Add a drizzle of oil to a cast-iron skillet and preheat the skillet over medium-high. Sear on each side for 2-3 minutes
Move sirloin steak to a clean plate tented with foil. Rest for 5-10 minutes