1. Trim the tenderloin of any excess fat and remove the silver skin.
2. Place the tenderloin and the pineapple juice in a resealable plastic bag. Press out any excess air and seal the bag. Marinate in the refrigerator for 2 hours or overnight.
3. Remove the meat from the refrigerator 30 minutes to 1 hour before grilling and allow it to sit on the counter to take off the chill.
4. In a small bowl, mix together the spice rub ingredients.
5. Remove the pork tenderloin from the resealable plastic bag and pat it dry with paper towels. Discard the marinade.
6. Rub or brush the tenderloin with the olive oil and then season it with the spice rub, massaging it into the meat.

If using a gas grill

1. When ready to cook, clean and oil the grill grates, then heat the grill to medium-high heat, about 400 degrees Fahrenheit.
2. Place the tenderloin on the grill and cook for about 8-10 minutes, turning on all sides to brown evenly. Lower the heat to medium, cover the grill and cook for about 5-6 minutes checking the pork a few times to make sure it's not charring too much. Grill until the pork reaches an internal temperature of 145 degrees Fahrenheit when checked with a meat thermometer.
3. Remove the pork from the grill and allow to rest, tented with aluminum foil for 10 minutes before slicing and serving.

If using a charcoal grill

1. Clean and oil the grates. Light a chimney with enough charcoal to cover half of the grill (Fill a charcoal chimney ¾ full). When all charcoal is lit and covered with gray ash, pour out the coals on one side of the grill, leaving the other side empty. This creates 2-zones, a zone of direct heat and a zone for indirect heat. Set the clean and oiled cooking grate in place, cover the grill, and allow to preheat for about 5 minutes.
2. Place the tenderloin on the grill and cook for about 8-10 minutes, turning on all sides to brown evenly. Move the pork to the cooler side of the grill (the side that is not lit). Grill for 6-7 minutes under indirect heat. Grill, covered flipping a few times until the pork reaches an internal temperature of 145 degrees Fahrenheit when checked with a meat thermometer.
3. Remove the pork from the grill and allow to rest, tented with aluminum foil for 10 minutes before slicing and serving.