Preheat your air fryer to 375°F (190°C) for 5 minutes.

Pat the pork tenderloin dry with paper towels. Rub the tenderloin with olive oil, then season generously with garlic powder, onion powder, paprika, salt, and pepper. Set aside.

In a medium pan, melt butter over medium heat. Add the chopped apple, onion, and celery, and sauté for 3-4 minutes until softened. Stir in cinnamon, nutmeg, salt, and pepper, then add the cubed bread. Pour in the chicken broth, stir to combine, and let the mixture sit for 1-2 minutes to allow the bread to absorb the liquid.

Using a sharp knife, carefully make a slit along the length of the pork tenderloin to create a pocket for the stuffing. Stuff the pork with the apple mixture and secure the opening with toothpicks if needed.

Place the stuffed pork tenderloin into the preheated air fryer basket. Cook at 375°F (190°C) for 25-30 minutes, or until the internal temperature reaches 145°F (63°C) when checked with a meat thermometer.

Let the pork tenderloin rest for 5 minutes before slicing. Remove the toothpicks and serve with extra stuffing on the side.