Place the chicken breast between two pieces of parchment paper and pound to an even half-inch thickness.
In a shallow bowl, soak the chicken in buttermilk for at least 30 minutes in the refrigerator.
In a separate shallow dish, whisk together the whole wheat flour, smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting any excess drip off, then dredge it through the flour mixture, pressing firmly to ensure an even coating.
Lightly brush or spray the coated chicken with avocado oil and place it in the air fryer basket.
Air fry at 375°F for 12 to 15 minutes, flipping halfway through, until the exterior is crispy and the internal temperature reaches 165°F.
Toast the whole grain bun and assemble the sandwich with the crispy chicken, lettuce, tomato, and pickles.