To a large bowl, add the buttermilk, 1 tsp salt, 1 tsp chili powder, granulated garlic, and onion powder. Mix well. Add the chicken breasts to the buttermilk mixture and let it sit at room temperature for 20 minutes.
In a small bowl, combine the mayo, 1/2 tsp paprika, 1/2 tsp chili powder, and 1/4 tsp cayenne pepper. Set aside.
Add the flour, 1 tsp salt, 1 tsp chili powder, 1/2 tsp baking powder, and 1/2 tsp cayenne pepper to a dish. Mix well.
Coat the chicken on each side with the seasoned flour. Make sure to coat well. Shake off any excess flour and set aside.
Heat some vegetable oil in a cast-iron skillet to 350 degrees F. Right before frying the chicken, coat the chicken in the remaining seasoned flour on both sides. Make sure to coat the chicken well on both sides. Fry the chicken for 4 minutes on each side or until the chicken reaches an internal temperature of 165 degrees f.
Once the chicken is done frying, let it rest on a wire rack for 5 minutes.
Serve on toasted brioche buns with spicy mayo and pickles.