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 for at least 20 minutes in the refrigerator.
In a separate shallow dish, whisk together panko, almond flour, smoked paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, and dredge thoroughly in the breadcrumb mixture, pressing firmly to ensure an even coating.
Lightly mist the chicken with avocado oil and place in an air fryer at 375°F for 12 to 15 minutes, flipping halfway through, until the exterior is golden and the internal temperature reaches 165°F.
Toast the whole-grain bun in a dry pan until lightly browned.
Assemble the sandwich by spreading Greek yogurt on the bottom bun, followed by the lettuce, tomato, crispy chicken breast, and pickles.