Place the chicken breast in a shallow bowl and pour the buttermilk over it, allowing it to marinate for at least 20 minutes to tenderize.
In a separate small bowl, whisk together the almond flour, smoked paprika, garlic powder, onion powder, sea salt, and black pepper until well combined.
Remove the chicken from the buttermilk, letting any excess liquid drip off, then dredge it thoroughly in the almond flour spice mixture until fully coated.
Lightly coat the breaded chicken on all sides with avocado oil using a mister to ensure the crust becomes golden and crisp.
Place the chicken in the air fryer at 375°F for 12 to 15 minutes, flipping halfway through, until the exterior is crunchy and the internal temperature reaches 165°F.
Toast the whole wheat bun until lightly browned and spread the plain Greek yogurt onto the bottom half as a creamy base.
Layer the romaine lettuce, tomato slices, and dill pickles onto the bun before topping with the hot crispy chicken and closing the sandwich.