Remove steaks from the fridge 1-2 hours prior to cooking. Allow them to come to room temperature.
Preheat the oven to 300°F with the rack in the middle of the oven. You could also use a grill or pellet smoker for this step (set for indirect heat at 300°F).
On a sheet tray with a cooling rack, salt and pepper the steaks 30 minutes prior to cooking.
Place the meat into the oven and cook until the internal temperature in the middle of the steak is 120 degrees. This can range from 8-20 minutes, depending on the thickness of the steak and your oven. Cook to temperature, not time. Remove the steaks and let them rest for 10 minutes.
Place a heavy bottom pan over high heat. When it smokes, add 1 teaspoon of the oil and brush it around the bottom of the pan with a basting brush. Add the steaks, as far apart from each other as you can. Sear each side for 1-2 minutes to get the perfect golden-brown color. Remove the steaks and set aside.
Turn the heat off and let the pan cool down for a few moments. Bruise the rosemary with the back of a knife. Then add it to the pan along with the butter and garlic. Once the butter is melted, add the steaks back in. Using a spoon or small ladle, baste the steak with the butter. Do this for a few minutes until the garlic and rosemary become really fragrant.
Remove the steak and allow to rest for 10 minutes. Slice and arrange on a platter for serving. Spoon some of the remaining butter over the steak. Finish with a light sprinkle of flaky finishing salt.