Trim and tie the tenderloin by removing any fat and silver skin.
Fold the tail end under and secure with kitchen twine at 1-inch intervals.
Add a generous sprinkling of kosher salt and black pepper over the meat.
Preheat your oven to 500°F.
Let the tenderloin sit at room temperature for about an hour.
This allows the flavors to come together beautifully.
Once the oven is heated, place the tenderloin on a lined baking sheet.
Spread softened butter evenly over the top.
Let it roast in the oven until desired doneness.
While the beef cooks, mix sour cream, horseradish, Dijon mustard, and chives in a small bowl.
Season with salt and pepper to your taste.
Allow the mixture to chill in the fridge while the beef finishes in the oven.
After the beef is cooked, let it rest for at least 15 minutes before slicing.
Serve with the horseradish sour cream on the side.