Place the chicken breast in a shallow bowl and pour the buttermilk over it, ensuring it is fully submerged. Marinate in the refrigerator for at least 30 minutes.
In a separate small 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 any excess drip off, and dredge it thoroughly in the seasoned flour mixture until evenly coated.
Preheat your air fryer to 375°F. Lightly brush or spray the coated chicken with avocado oil to ensure a golden, crispy finish.
Place the chicken in the air fryer basket and cook for 12-15 minutes, flipping halfway through, until the internal temperature reaches 165°F.
While the chicken cooks, lightly toast the sprouted grain bun in a pan or toaster.
Assemble the sandwich by placing the crispy chicken on the bottom bun, followed by the lettuce, tomato slices, and pickles, then top with the other half of the bun.