Place the chicken breast between two pieces of parchment paper and pound to an even half-inch thickness.
Submerge the chicken in buttermilk in a small bowl and let it marinate for 15 to 20 minutes.
In a separate shallow dish, whisk together the whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, then dredge thoroughly in the seasoned flour mixture.
Lightly coat the breaded chicken on both sides with avocado oil using a kitchen sprayer or brush.
Place the chicken in an air fryer basket and cook at 375°F for 12-15 minutes, flipping halfway, until the exterior is a golden crunch.
While the chicken cooks, lightly toast the whole wheat bun in a dry pan or toaster.
Assemble the sandwich by placing the lettuce on the bottom bun, followed by the crispy chicken and the dill pickles.