Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
Submerge the chicken in buttermilk in a shallow bowl and marinate in the refrigerator for at least 30 minutes.
In a separate bowl, whisk together the whole wheat flour, 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 brush or spray both sides of the coated chicken with avocado oil.
Place the chicken in an air fryer basket and cook at 375°F for 12 to 15 minutes, flipping halfway through, until the exterior is golden and crispy.
Toast the whole grain bun in a dry pan or the air fryer for 1 minute until warm.
Assemble the sandwich by placing the lettuce on the bottom bun, followed by the crispy chicken and dill pickles.