Place the chicken breast between parchment paper and pound to an even half-inch thickness.
In a shallow bowl, combine the buttermilk with the sea salt and black pepper, then submerge the chicken to marinate for at least 15 minutes.
In another bowl, whisk together the whole wheat flour, smoked paprika, garlic powder, and onion powder.
Remove the chicken from the buttermilk, letting excess drip off, and dredge thoroughly in the flour mixture.
Lightly coat the air fryer basket with avocado oil and place the chicken inside.
Air fry at 375°F for 12-15 minutes, flipping halfway through, until the exterior is golden and the internal temperature reaches 165°F.
Toast the whole grain bun until lightly browned.
Assemble the sandwich by layering the crispy chicken, lettuce, tomato, and pickles on the toasted bun.