Prepare the Beef: Pat the beef tenderloin dry with paper towels. Season generously with Salt and Black Pepper from the Beef ingredients list. Heat Olive Oil from the Beef ingredients list in a large, oven-safe skillet over high heat until smoking. Sear the beef on all sides until deeply browned, about 2-3 minutes per side. Transfer to a plate and let cool slightly. Once cooled, spread Dijon Mustard evenly over all sides of the beef. Place in the refrigerator to chill for at least 30 minutes.