Place the chicken breast in a bowl and cover with buttermilk, letting it marinate for at least 15 minutes.
In a shallow dish, whisk together the almond flour, arrowroot powder, garlic powder, onion powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, then dredge thoroughly in the flour mixture until fully coated.
Lightly coat the air fryer basket with avocado oil and place the chicken inside, spraying the top of the chicken with the remaining oil.
Air fry at 375°F for 12-15 minutes, flipping halfway through, until the coating is golden and the internal temperature reaches 165°F.
Toast the whole wheat bun until lightly browned and assemble the sandwich with the crispy chicken, butter lettuce, tomato slices, and pickles.