Begin by marinating your chicken tenderloins. If using buttermilk, combine it with 2 tablespoons of mayo, and mix well. Add the chicken tenderloins to the bowl, ensuring they are well coated. Cover and refrigerate for at least 30 minutes (or up to overnight) to allow the flavors to meld and the chicken to tenderize.
While the chicken is marinating, set up your breading station. In one bowl, whisk together the egg, Dijon mustard, 2 tablespoons of mayo, and the yellow mustard, lemon juice, and honey until smooth. In a separate bowl, mix together the flour, garlic powder, paprika, salt, onion powder, and pepper. Finally, in a third bowl, combine the panko breadcrumbs and cornmeal.
Remove the marinated chicken from the fridge. One by one, dip each tenderloin into the flour mixture, ensuring it is fully coated. Shake off any excess flour, then dip it into the egg mixture, allowing any excess to drip off. Finally, coat the chicken in the panko-cornmeal mixture, pressing lightly to ensure the breadcrumbs adhere well.
Preheat your air fryer to 400°F (200°C). Lightly spray the air fryer basket with cooking spray to prevent sticking. Arrange the breaded chicken tenders in a single layer in the basket, making sure they are not overcrowded. Spray the tops lightly with cooking spray for extra crispiness. Cook for 10-12 minutes, flipping halfway through, until the chicken is golden brown and reaches an internal temperature of 165°F (74°C).
Once cooked, remove the chicken tenders from the air fryer and let them rest for a few minutes. Serve them with your favorite dipping sauces, like honey BBQ sauce, or enjoy them on a salad or in a sandwich.