Remove the beef tenderloin from the refrigerator 1 hour before cooking to let it come to room temperature. Preheat oven to 425°F (220°C).

Pat the beef dry with paper towels. Rub all over with olive oil, then season generously with the kosher salt and coarse black pepper, pressing the pepper into the meat.

In a small saucepan over medium heat, combine balsamic vinegar, soy sauce, brown sugar, minced garlic, and Dijon mustard. Simmer for 5-7 minutes until the mixture thickens into a syrup-like glaze. Set aside.

Place the beef on a rack in a roasting pan. Roast in the preheated oven for approximately 15 minutes.

Remove the roast briefly and brush generously with half of the glaze. Return to the oven and roast for another 15-20 minutes, or until an instant-read thermometer inserted into the thickest part reads 125°F for medium-rare.

Brush the remaining glaze over the beef during the last 5 minutes of cooking if desired, or reserve it for serving.

Transfer the beef to a cutting board and tent loosely with foil. Let it rest for at least 15 minutes to allow juices to redistribute.

Slice into thick medallions and serve warm.