Place the chicken breast in a bowl and cover with buttermilk; marinate for at least 15 minutes to ensure a juicy interior.
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 excess to drip off, then dredge thoroughly in the seasoned flour mixture.
Lightly coat the breaded chicken with avocado oil and place it in the air fryer basket.
Air fry at 375°F for 12-15 minutes, flipping halfway through, until the coating is golden and the chicken is cooked through.
Toast the whole wheat bun and assemble the sandwich with the crispy chicken, romaine lettuce, tomato slices, and pickle chips.