Pound the chicken breast between two pieces of parchment paper to an even half-inch thickness.
Place the chicken in a bowl with the buttermilk and let it marinate for at least 30 minutes in the refrigerator.
In a shallow dish, whisk together the whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, allowing the excess to drip off, and dredge it thoroughly in the seasoned flour mixture.
Lightly spray or brush the chicken and the air fryer basket with avocado oil.
Air fry at 375°F for 12 to 15 minutes, flipping halfway through, until the coating is golden brown and the internal temperature reaches 165°F.
Lightly toast the whole wheat bun in a dry pan or the air fryer for 1 minute.
Assemble the sandwich by placing the crispy chicken on the bottom bun, followed by lettuce, tomato slices, and pickles.