Slice the chicken breast into even strips or medallions to ensure uniform cooking.
Place the chicken in a shallow bowl and pour the buttermilk over it, ensuring every piece is submerged. Let it marinate in the refrigerator for at least 30 minutes.
In a separate wide dish, whisk together the arrowroot starch, smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Preheat your air fryer to 400°F (200°C).
Remove each piece of chicken from the buttermilk, letting the excess drip off, then dredge thoroughly in the arrowroot spice mixture until well-coated.
Lightly spray the air fryer basket with avocado oil. Place the chicken in the basket in a single layer, ensuring they do not touch.
Mist the top of the chicken generously with the remaining avocado oil to help the arrowroot develop a golden crust.
Air fry for 12-15 minutes, flipping halfway through and adding another light mist of oil if any dry white spots remain, until the internal temperature reaches 165°F.
Let the chicken rest for 2 minutes before serving to maintain its juiciness.