Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
Place the chicken in a shallow bowl and pour the buttermilk over it, ensuring it is fully coated; let it marinate for 10 minutes.
In a separate shallow dish, whisk together the flour, garlic powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, then dredge it in the flour mixture, pressing firmly to create a thick coating.
Heat the avocado oil in a non-stick skillet over medium heat.
Add the chicken to the skillet and cook for 5-6 minutes per side until the exterior is golden brown and the internal temperature reaches 165 degrees Fahrenheit.
While the chicken rests, lightly toast the whole wheat bun in the same skillet.
Assemble the sandwich by placing the lettuce on the bottom bun, followed by the crispy chicken and the dill pickles.