Marinate the Chicken: In a large bowl, combine buttermilk, garlic powder, salt, and pepper. Add the chicken tenderloins and ensure they are fully submerged. Cover and refrigerate for at least 30 minutes, or up to 4 hours.
Prepare the Breading: In a separate bowl, combine panko breadcrumbs (or regular breadcrumbs), Parmesan cheese (if using), smoked paprika, garlic powder, onion powder, salt, and pepper. Mix well.
Coat the Chicken: Remove chicken tenderloins from the buttermilk marinade and let any excess drip off. Dredge each tenderloin in the breadcrumb mixture, ensuring they are fully coated. Press the breadcrumbs gently to adhere.
Preheat and Cook: Preheat your air fryer to 400°F (200°C). Lightly spray the air fryer basket with cooking spray. Arrange the breaded chicken tenderloins in a single layer in the basket, ensuring they are not overcrowded. You may need to cook in batches.
Cook: Cook for 10-12 minutes, flipping halfway through, until the chicken is golden brown and cooked through. The internal temperature should reach 165°F (74°C).
Serve: Let the chicken tenders rest for a few minutes before serving.