Remove steaks from refrigerator 15 to 20 minutes before cooking to bring them to room temperature.

Preheat a 12-inch cast iron skillet over high heat for 5 minutes until it is extremely hot.

Pat steaks completely dry with paper towels to remove surface moisture.

Season each steak with 1 teaspoon kosher salt and 1/2 teaspoon freshly ground black pepper on both sides.

Drizzle a small amount of high-heat oil into the hot skillet, then place steaks in the pan and sear undisturbed for 4 to 5 minutes.

Flip steaks once and immediately add 1 tablespoon butter, smashed garlic cloves, and rosemary sprigs; cook for 3 to 4 minutes.

Insert an instant-read thermometer into the thickest part of each steak; remove from heat at 130 to 135°F for medium-rare.

Transfer steaks to a cutting board and let rest for 5 minutes to allow juices to redistribute.