Pat the beef down with paper towels. When dried, coat the beef evenly with the steak seasoning and rub all over.Fold the narrow end of the tenderloin back under itself in order to create a relatively even thickness along the entire length of the tenderloin.Tie the tenderloin at one-inch intervals using butcher’s twine.
Place the tenderloin on a cooling rack on top of a baking pan and place it uncovered in the fridge overnight. Yes, uncovered. When ready to make remove the tenderloin from the fridge and place on the counter to come to room temperature.
Preheat oven to 425F, rack in the middle.Line a baking pan with foil and place a cooling rack in it.
Heat a cast iron or stainless steel pan over medium-high heat. Add in the bacon grease.
When the grease is melted add in the tenderloin. Step back as it’ll spit up grease to quick sear the outside. Pan sear for 6-8 minutes on each side. When all sides are browned, place the beef on the cooling rack and evenly spread the butter on top. Place the pan in the oven and bake for 15-25 minutes or until desired consistency. 120F for medium rare (15-20 minutes), 130F for medium (20-25 minutes). Remove the pan from the oven and transfer the beef to a carving board. Tent with foil and rest for 10-15 minutes.