Set steak at room temperature and pat dry with paper towels. Sprinkle both sides with kosher salt and let sit for 15-30 minutes. When ready to cook, heat a 12-inch cast iron pan on the stove top to medium/medium-high heat. Add olive oil and tilt pan so oil covers surface. It should be hot and shimmery.

Blot steak once again on both sides with paper towels and then sprinkle liberally with black pepper, and lightly with a little more kosher salt.

Place steak in pan and sear for about 2 minutes, then flip and sear other side. After flipping the first time, add the butter to the pan and add in the rosemary and garlic. Reduce heat to medium, or medium low if necessary (butter should still sizzle and foam, but not burn). Use a spoon to spoon up butter and ladle over steak (carefully use a potholder or towel to handle pan, tipping if necessary to spoon butter). Continue basting in butter, flipping occasionally so you are basting both sides, until steak reaches an internal temperature of 130-135 for rare, 135-140 for medium rare. We recommend you do not cook past 150 degrees. Remove steak from pan and place on cutting board, tented with foil. Let rest 5 minutes and then serve with pan sauce spooned over the top.