In a small bowl, combine brown sugar, smoked paprika, kosher salt, chili powder, onion powder and garlic powder.
Trim the pork tenderloin of any excess fat and silverskin. Pat the pork dry, and then rub the spice mixture all over the meat.
Allow pork to sit at room temperature while preparing the grill. Preheat grill to medium heat and brush the grates with vegetable oil (to prevent sticking). Place pork on the grill. Close the grill and cook 15-18 minutes, turning every few minutes to ensure even cooking. The meat is done when it reaches an internal temperature of 140-145 degrees F. You can baste with the barbecue sauce during the final 1-2 minutes, or just serve warm barbecue sauce alongside the pork for dipping.
Remove the tenderloin to a cutting board and allow the meat to rest for about 5-10 minutes before slicing and serving.
Notes
Thesalt and sugar are necessary for seasoning the meat and for encouraging caramelization on the outside. You can adjust the other spices to suit your taste. For instance, substitute regular paprika for the smoked paprika, or add a dash of cayenne for a spicy rub.
Asingle pork tenderloin is typically just 1 lb. of meat, making it an appropriate amount of food for 2-4 people (depending on the size of your appetite). If you're feeding a larger family of 4-5, I recommend doubling all of the ingredients and cooking two tenderloins side-by-side on the grill.
Prep ahead! The tenderloin can be trimmed and rubbed up to 24 hours in advance. Remove from the refrigerator 30 minutes before grilling.