Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness to ensure even cooking.
Submerge the chicken in buttermilk in a shallow bowl, ensuring it is fully coated, and marinate for at least 15 minutes.
In a separate shallow dish, whisk together the flour, paprika, garlic powder, salt, and pepper until well combined.
Remove the chicken from the buttermilk, letting excess drip off, then dredge thoroughly in the flour mixture, pressing to adhere.
Heat avocado oil in a cast-iron skillet over medium-high heat until the oil is shimmering and hot.
Carefully place the chicken in the skillet and cook for 5-6 minutes per side until the crust is golden and the internal temperature reaches 165°F.
Toast the sprouted bun in the same skillet for 1 minute until the edges are lightly browned and fragrant.
Spread Greek yogurt on the bottom bun, layer with lettuce, tomato, and the crispy chicken, then top with the remaining bun.