Bring steaks to room temperature before cooking. (This allows for a more even cook all the way through).
Pat them dry with paper towels.
Heat oil in a large cast-iron skillet over medium high heat.
Once the oil is hot, season steaks with salt, pepper and Cajun Creole seasoning on both sides and add to the skillet. Cook for about 2 minutes each side or until you get a nice brown crust. Turn the steaks on their sides to sear the edges (about 1 minute).
Reduce the heat to medium low. Add the butter, garlic and rosemary sprigs. Cook garlic and rosemary for about 1 minute to release flavors.
Baste the steaks with the butter for a minute or until they are 10-degrees from your desired doneness. The temperature will rise while steaks rest. Use instant-read thermometer to check for doneness.
Transfer steaks to a cutting board, cover with foil and allow to rest for 10 minutes before slicing.
Serve steaks with pan juices.
Be sure to pat your steaks dry before cooking as dry meat forms the best crust.
Season steaks JUST before cooking. It guarantees perfect browning.
Keep leftovers in a sealed container in the fridge for up to 3 days.