Place the chicken breast in a shallow bowl and cover with buttermilk, marinating for at least 20 minutes in the refrigerator.
In a separate small bowl, combine the almond flour, panko breadcrumbs, sea salt, black pepper, garlic powder, and smoked paprika.
Remove the chicken from the buttermilk, letting any excess drip off, then dredge through the breading mixture, pressing firmly to ensure an even coating.
Lightly coat the breaded chicken on both sides with avocado oil spray and place in the air fryer basket.
Air fry at 375°F for 12 to 15 minutes, flipping halfway through, until the exterior is golden brown and the internal temperature reaches 165°F.
While the chicken cooks, whisk together the Greek yogurt and Dijon mustard to create a clean-eating sandwich spread.
Toast the whole grain bun until lightly crisp, then assemble the sandwich with the yogurt sauce, butter lettuce, crispy chicken, and dill pickles.