1. Bring the beef tenderloin to room temperature and preheat the oven to 425°F (220°C).

2. Pat the tenderloin dry and rub with olive oil, salt, pepper, minced garlic, and chopped herbs.

3. Heat a cast iron skillet over high heat and sear the tenderloin on all sides until golden brown, about 3–4 minutes per side.

4. Transfer the seared beef to a roasting pan with a rack and insert a meat thermometer into the thickest part.

5. Roast until the internal temperature reaches 130°F (54°C) for medium-rare, about 25–30 minutes.

6. Remove the tenderloin from the oven, tent with foil, and let rest for 15 minutes before slicing.

7. Meanwhile whisk together prepared horseradish, sour cream, Dijon mustard, lemon juice, and heavy cream until smooth, then chill for 10 minutes.

8. Slice the tenderloin into medallions, arrange on a platter, and serve with the creamy horseradish sauce on the side.