Take your steaks out of the fridge about half an hour before you want to cook them. Season them liberally with kosher salt on both sides. Let them sit for 30 minutes.
Preheat your oven to 350 degrees Fahrenheit.
Heat a cast iron skillet, or other heavy-bottomed pan, over medium heat until it is very hot. If you do larger steaks, you may have to use 2 pans. If you use two pans I recommend staggering the cook times by starting one steak 2 or 3 minutes before the other, that way you can attend to both. Make sure that your pan is oven safe.
Add the olive oil. It may smoke. Don't be alarmed.
Immediately pat the steaks dry with a paper towel and add them to the pan, making sure to lay them in the pan away from your body.
Press the steaks into the pan to make sure the entire surface is making contact with the pan. Let the steaks cook on the first side for 4 minutes. Don't move them!
Using a pair of tongs, flip the steaks, and let them sear for about 2 minutes.
Add ½ cup of butter, the rosemary, and the garlic cloves to the pan. Tilt the pan toward you, so that the butter pools where you can reach it. Take a large spoon and pour the butter over the steaks repeatedly until the steaks reach 5 degrees below your desired temperature. For example, if you like your steak medium, pull the steak at 140 degrees. As it rests the temperature will rise to 145 degrees.
I highly, highly recommend using an instant read or probe thermometer for this recipe. Please.
If your steak is a long way from reaching your desired internal temperature after you baste for a few minutes, put a probe thermometer in it and put the whole pan in the oven.
Pull the steaks from the oven when they reach 5 degrees below your desired temperature. Refer to the temperature chart in the post for doneness temperatures. If you do not have a probe thermometer, check your steaks with an instant read thermometer after they've been in the oven for about 3 minutes by inserting the thermometer into the center of a steak. It doesn't take long.
When your steaks have reached your desired temperature, put them on a cutting board and let them rest for 5 minutes. Add pepper, if desired, then slice and enjoy!
