1. Preheat the oven to 250°C.
2. Place the tenderloin on a roasting rack. Sprinkle generously with kosher salt and sugar, which will deepen the savory flavors.
3. Press the crushed peppercorns all over the surface of the meat. Insert a meat thermometer and place in the oven until the beef registers 50°C for medium-rare/rare. Beef will probably cook in 20 to 25 minutes depending on its temp before it goes in the oven.
4. While the meat is roasting, melt the butter with the garlic in a small skillet, and allow the butter to slightly brown. Remove the garlic and discard.
5. Remove the meat when it's done and pour the garlic butter over gently (it should sizzle when it hits the meat). Cover the meat loosely with foil and allow to rest for 10 minutes before slicing.