Pre-heat oven to 425 degrees F

Pat the beef tenderloin dry with paper towels. The drier the beef, the better crust it will form

Rub oil on beef tenderloin and form a crust with salt and pepper on all sides of the beef

Pre-heat cast iron* pan on medium-high heat for 2 minutes

*see note above if you do not have a cast iron pan

Place beef tenderloin in a hot pan and sear on all sides until a golden crust forms. You can wrap your tenderloin or cut it into two pieces to sear

Once the beef has seared on all sides, place it onto a baking tray and top with cubes of butter and rosemary sprigs. The butter and rosemary should be evenly spread across the top

Bake in a 425 degree oven until the internal temperature reads 10 below your desired internal temperature (e.g. if you want a medium rare at 135, bake until reads 125). The steak will come up about 10 degrees as it rests

When it reads 10 degrees below, remove the steak from the oven and tent gently with foil. Allow it to rest for at least 15 minutes

Slice the steak and top with juices from the pan