Place the chicken breast between two sheets of parchment paper and pound to an even thickness of about half an inch.
In a shallow bowl, soak the chicken in buttermilk for at least 15 minutes to tenderize.
In a separate shallow dish, whisk together the whole wheat flour, smoked paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge thoroughly in the seasoned flour mixture.
Heat the avocado oil in a cast-iron skillet or non-stick pan over medium-high heat.
Carefully place the chicken in the hot oil and cook for 4-5 minutes per side until the crust is golden brown and the internal temperature reaches 165°F.
While the chicken rests, lightly toast the whole grain bun in the same pan or a toaster.
Assemble the sandwich by placing the lettuce and tomato on the bottom bun, followed by the crispy chicken and dill pickle slices.
Top with the remaining bun half and serve immediately.