Pat the turkey tenderloin pieces completely dry with paper towels. This step is important for getting a nice golden sear in the air fryer.
In a small bowl, stir together the olive oil and dijon mustard until smooth. In a separate small bowl, combine the smoked paprika, garlic powder, onion powder, dried thyme, dried rosemary, salt, and black pepper.
Brush the mustard mixture all over each piece of turkey tenderloin, coating every surface. Then sprinkle the spice blend generously over the turkey, pressing it gently so it adheres well.
Preheat the air fryer to 370 degrees F. Place the turkey tenderloins in the basket, leaving space between them for air circulation.
Air fry for 12 minutes, then carefully flip the tenderloins. Continue cooking for another 10 to 13 minutes until the internal temperature reaches 165 degrees F when checked with an instant-read thermometer at the thickest part.
Remove the turkey from the air fryer and transfer it to a cutting board. Tent loosely with foil and let it rest for 5 to 8 minutes. This resting time allows the juices to redistribute so the meat stays tender and moist.
Slice the turkey tenderloin against the grain into 1/2-inch thick medallions. Garnish with fresh parsley and serve.