Combine the brown sugar, paprika, chili powder, dried thyme, garlic powder, salt and pepper in a small bowl. Stir to mix.
Preheat air fryer to 380° F for 5 minutes.
Pat the pork tenderloin dry with paper towels. Use a sharp knife to remove the silver skin (the thin silver/white membrane). Rub the spice mixture over all sides of the meat.
Place pork in the preheated air fryer and cook at 380° F for 10 minutes. Then flip the tenderloin over and continue cooking for 8-16 more minutes, or until the center of the pork registers 145° F on an instant read thermometer.
Let the pork rest for 5 minutes before slicing and serving.
