Remove the steak from refrigerator 30-60 minutes before cooking, so they can reach room temperature for even cooking.
Position the oven rack in the middle and preheat oven to 425°F (218°C).
Place a large cast-iron skillet over high heat and allow to heat for 5 minutes until very hot. (You can also place in the preheated oven for 15 minutes.)
Remove any bits of bone and pat dry the steak with paper towels to remove excess moisture that could interfere with searing.
Rub on all sides with 1 tablespoon of olive oil.
Season both sides with salt and pepper.
Add the remaining 1 tablespoon oil to the pan and swirl to coat.
Carefully place the steak in the pan using kitchen tongs, laying them away from you to avoid splatter.
Sear the first side for 2 minutes.
Flip using kitchen tongs and sear the other side for 2 minutes.
Add garlic, butter and rosemary and then immediately transfer the pan to the oven.
Bake for 2-3 minutes without flipping for medium-rare steaks (130°F/54°C), checking doneness by inserting an instant-read meat thermometer (see recipe notes for other donenesses***).
Remove steak to a plate or cutting board covered with aluminum foil to rest for 5 minutes so the juices can retreat back into the meat.
To serve, cut the meat away from the bone and slice across the grain into strips.