- In a bowl, combine all the sauce ingredients. Rub the tenderloin with sauce; reserve the remaining sauce for basting. Refrigerate the tenderloin, ideally for 4 hours.
- Preheat the grill, setting the burners to medium. Centre the tenderloin lengthwise on the spit and adjust on the rotisserie.
- Start the rotisserie and close the cover. Baste with the marinade several times during cooking. Grill until a thermometer inserted in the meat reads 63°C (145°F).
- Transfer to a cutting board, tent loosely with foil and let rest for 15 minutes before slicing.