Place the chicken breast between two sheets of parchment paper and pound with a meat mallet to an even 1/2-inch thickness.
Submerge the chicken in a shallow bowl with the buttermilk and marinate in the refrigerator for at least 30 minutes to ensure a juicy interior.
In a separate wide dish, whisk together the whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge thoroughly in the flour mixture, pressing the coating firmly into the meat.
Lightly coat the air fryer basket with avocado oil spray, place the chicken inside, and spray the top of the chicken generously to ensure a crispy finish.
Air fry at 375°F for 12 to 15 minutes, flipping the chicken halfway through and applying another light spray of oil, until the coating is golden and the internal temperature reaches 165°F.
Lightly toast the whole wheat bun, then assemble the sandwich by layering the lettuce, crispy chicken, and dill pickles.