1 3 1⁄2–5 lb. fully trimmed
beef tenderloin, butt end left intact
2 tbsp. extra-virgin olive oil
Kosher salt, to taste
3 tbsp. dijon mustard
3 tbsp. cracked black peppercorns
2 tbsp. finely chopped fresh rosemary
2 tbsp. finely chopped fresh thyme
1 1⁄2 cups sour cream
3 tbsp. prepared horseradish
1. Put beef on a sheet of plastic wrap; rub with oil. Sprinkle with salt; rub with mustard, then season with pepper, rosemary, and thyme. Wrap in plastic wrap; let sit at room temperature for 1 hour.
2. Heat oven to 425˚. Place beef on a rack on a rimmed baking sheet. Roast until an instant-read thermometer inserted into thickest end reads 115˚, about 35 minutes. Switch oven to broiler setting; broil until crusty, 5–10 minutes. (A thermometer inserted into thickest end should read 125˚.) Let roast rest on a cutting board for 30 minutes. Meanwhile, combine sour cream and horseradish in a bowl to make a sauce. Thinly slice beef and serve with sauce.