Place the chicken breast between two sheets of parchment paper and pound with a meat mallet until it reaches an even half-inch thickness.
In a shallow bowl, submerge the chicken in the buttermilk and let it marinate for at least 15 minutes in the refrigerator.
In a separate shallow dish, whisk together the whole wheat flour, garlic powder, onion powder, sea salt, black pepper, and paprika.
Remove the chicken from the buttermilk, allowing excess to drip off, then dredge it in the flour mixture, pressing firmly so the coating adheres.
Heat the avocado oil in a cast-iron skillet or non-stick pan over medium-high heat until the oil is shimmering.
Carefully place the chicken in the pan and fry for 4 to 5 minutes per side until the crust is golden brown and the internal temperature reaches 165°F.
Remove the chicken and let it rest on a wire rack for 2 minutes while you lightly toast the whole grain bun in the same skillet.
Assemble the sandwich by placing the romaine lettuce on the bottom bun, followed by the crispy chicken and the dill pickles.