Place the chicken breast in a shallow bowl and pour the buttermilk over it, ensuring it is fully submerged; let it marinate for at least 15 minutes.
In a separate small bowl, whisk together 3 tablespoons of whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge it thoroughly in the seasoned flour mixture until evenly coated.
Heat the avocado oil in a large skillet over medium-high heat.
Add the chicken to the skillet and cook for 5-6 minutes per side, or until the exterior is golden brown and the internal temperature reaches 165 degrees Fahrenheit.
Remove the chicken from the pan and set aside on a plate.
In the same skillet, whisk the remaining teaspoon of flour into the pan drippings for 30 seconds, then slowly pour in the chicken broth while whisking constantly.
Simmer the broth for 2 minutes until slightly thickened, then remove from heat and stir in the Greek yogurt until the gravy is smooth and creamy.
Pour the warm gravy over the chicken and serve immediately.