Trim the pork tenderloin of any excess fat and silver skin.
Put the lime zest, lime juice, honey, salt, and garlic powder in a small, lidded jar and shake to combine. Pour half of this marinade into a 1-gallon zip-top bag, add the chipotle pepper, and slosh around to combine. Add the pork tenderloin to the bag and seal, removing as much air as possible, and place in a container to catch any leaks. Marinate in the refrigerator for 6 to 24 hours, flipping the bag halfway through. Place the remaining marinade in a covered container and refrigerate until ready to use.
Remove the tenderloin from the bag and allow to sit at room temperature while preparing the grill. Remove the reserved marinade from the refrigerator.
Fill a large chimney starter with natural lump charcoal and light it. Once the charcoal is ashy and white, about 30 minutes, dump the hot charcoal onto the lowest grate of the grill and spread into an even layer using extra-long tongs. Place the cooking grate back on the grill and cover with the lid; heat the grate to medium heat for 2 to 3 minutes.
Brush the grill with vegetable oil. Remove the tenderloin from the bag and place in the center of grate. Discard bag with marinade. Cover and cook until the tenderloin reaches an internal temperature of 140ºF, turning every 1 1/2 to 2 minutes, about 12 to 15 minutes total.
Remove the tenderloin from the grill and place on a large piece of heavy-duty aluminum foil folded at the edges to create a basket, and pour on the reserved marinade. Wrap tightly and rest for 10 minutes. Remove to a cutting board and slice. Garnish with cilantro and serve.