Start by placing the beef tenderloin on a cutting board. Using a sharp knife, trim away any silver skin and excess fat. This ensures that your tenderloin cooks evenly and remains tender.

Marinate (Optional, but recommended): In a small mixing bowl, combine soy sauce, Worcestershire sauce, bourbon (if using), minced garlic, and brown sugar. Place the trimmed tenderloin in a large resealable plastic bag and pour the marinade over it. Seal the bag, ensuring the tenderloin is fully coated. Marinate in the refrigerator for at least 2 hours, or overnight for the best flavor.

Remove the tenderloin from the marinade and pat it dry with paper towels. Rub the entire surface of the tenderloin with olive oil. In a small bowl, mix kosher salt, black pepper, garlic powder, onion powder, dried thyme, and dried rosemary. Generously season the tenderloin on all sides with this mixture.

For a charcoal grill: Light your charcoal using a chimney starter. Once the coals are ashed over, place them on one side of the grill, leaving the other side empty for indirect cooking. Place a drip pan filled with a bit of water on the empty side to catch drippings and add moisture to the grill.

For a gas grill: Preheat your grill by turning on only half of the burners to create zones of direct and indirect heat. Place a drip pan underneath the grate on the cooler side of the grill.

Place a couple of oak or hickory wood chunks directly on the hot coals (for a charcoal grill) or in a smoker box (for a gas grill). If you’re feeling adventurous, add a small chunk of cherry wood for a touch of sweetness.

Place the seasoned beef tenderloin on the cooler side of the grill, directly over the drip pan. Close the lid and adjust the vents (for charcoal) or temperature (for gas) to maintain a steady 225°F. Let the tenderloin smoke slowly, checking the temperature occasionally.

While the tenderloin smokes, melt the butter in a small bowl. Stir in minced garlic, chopped rosemary, and thyme. Set aside.

About 1.5 hours into smoking, start basting the tenderloin with the garlic-herb butter every 30 minutes. This will add a rich, savory flavor and help keep the meat moist.

Once the internal temperature of the tenderloin reaches around 125°F (for medium-rare), move it over to the direct heat side of the grill. Sear each side for 2-3 minutes until a nice crust forms.

Remove the tenderloin from the grill and loosely tent it with aluminum foil. Let it rest for at least 10 minutes before slicing. This allows the juices to redistribute throughout the meat, ensuring every bite is juicy and flavorful.