Coat steak with coarse salt and let sit for at least 15 minutes, up to 2 hours. The salt brings out moisture which allows for a better sear. You should blot the steak with a paper towel before cooking. Bring steak to room temperature. Preheat the oven to 425°. Heat cast iron pan on high heat over the stove. Melt 1-2 tbsp of butter in the bottom of the pan. Gently lay the steak in the pan and cook for 4 minutes. Flip the steak and cook again for 4 minutes. Put into a hot oven until desired doneness. Cooking time will vary based on the thickness of the steak. (If you are using a thin steak you may not need to place in the oven if you like it rare to medium rare) When you finish cooking let it rest for at least 3 minutes.