Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
In a shallow bowl, submerge the chicken in the buttermilk and let it marinate for 15 minutes to tenderize.
In a separate shallow dish, whisk together the flour, smoked paprika, garlic powder, salt, and pepper.
Remove the chicken from the buttermilk, letting the excess drip off, and dredge thoroughly in the seasoned flour mixture.
Heat the avocado oil in a cast-iron skillet over medium-high heat until shimmering.
Carefully place the chicken in the skillet and cook for 5 to 6 minutes per side until the crust is golden brown and the internal temperature reaches 165°F.
During the last minute of cooking, place the bun halves cut-side down in the pan to lightly toast them.
Assemble the sandwich by placing the lettuce on the bottom bun, followed by the crispy chicken and the pickle slices.