If you plan to chill your tenderloin overnight: Remove the tenderloin from the refrigerator and pat dry with paper towels. Season with salt and pepper and tie the roast with kitchen twine spaced approximately 1-inch apart (see notes). Chill in the refrigerator uncovered for at least 12 hours or overnight. Remove at least 1 hour before roasting to get the tenderloin to room temperature.
If you do not plan to marinate overnight: Remove tenderloin from the refrigerator at least 1 hour before you plan to cook and allow it to rest at room temperature. Tie up the tenderloin and season with salt and pepper.
Preheat the oven to 430 F / 220 C and place the baking rack in the middle of the oven.
Meanwhile, place the room temperature tenderloin in a roasting pan and rub the softened butter all over the beef (if your beef is too cold the butter will solidify).
Heat a large cast-iron skillet over medium-high heat. Once the pan is hot, add a tablespoon of oil and sear the tenderloin on all 4 sides, approximately 3 minutes on each side, or until golden brown.
Transfer the seared tenderloin back to the roasting pan (reserve the cast-iron skillet, we'll be using that again in a minute) or a baking sheet and place the seared tenderloin in the preheated oven.
Cook to your desired doneness (rare, medium-rare, or medium). It will take approximately 20 minutes to reach an internal temperature between 120 - 125 °F (medium-rare) as read using a digital meat thermometer.
Remove the roast and allow it to rest for about 15 minutes before slicing.
Serve with the red wine sauce (recipe instructions below).