For Beef Tenderloin:

1. Pull out beef tenderloin 1 hour before cooking.
2. Preheat oven to 325 degrees F.
3. Generously season both sides of prepared beef tenderloin with salt & pepper. (see notes for how to trim & prepare)
4. Heat a large cast iron skillet to medium high heat. You want it searing hot!
5. Add grape seed oil to the skillet and immediately add prepared beef tenderloin.
6. Sear each side for 2-3 minutes, until lightly browned. (you’ll do this to all four sides)
7. Then add butter, garlic and fresh thyme to the pan.
8. Carefully, tilt pan towards you so the melted butter gathers at the bottom.  Spoon the melted butter over the beef tenderloin, do this for about 1 minute.
9. Place cast iron skillet in the preheated oven, uncovered. Roast beef tenderloin for 35-40 minutes.(Medium Rare 125 – 130 degrees F  | Medium 130 – 135 degrees F  | Medium Well 135 – 140 degrees F)
10. Once it reaches your desired doneness. Remove the pan from the oven and place the tenderloin on a cutting board. Let it rest for 10 minutes, this will allow the juices to recirculate.

Fresh Herb Crust:

1. To a small bowl add fresh parsley, fresh basil and fresh thyme. Mix them together.
2. Once tenderloin has rested for 10 minutes, you can either roll the tenderloin in the fresh herbs to coat or using your hands press the fresh herbs onto the tenderloin. (I found the later to be easier)

For Horseradish Sauce:

1. Add mayo, prepared horseradish, whole grain mustard and garlic clove to a small bowl. Mix together until the sauce is combined. Set aside.
2. Slice tenderloin and serve with horseradish sauce.