In a medium bowl, add the salt, pepper, onion powder, garlic powder, paprika, cumin, oregano, and cayenne and mix until combined. In a another medium bowl, combine half of the spice mix with the flour, mixing until the spices are evenly distributed.
Add the chicken to a large bowl and sprinkle with the remaining spice blend. Mix until all the chicken pieces are evenly coated.
Pour the buttermilk over the chicken and stir until the residual spices from the chicken have blended in with the buttermilk to create a light orange color. Marinate the chicken in the fridge for 2 hours, or overnight.
Heat the oil to about 325°F (160°C) in a large cast-iron skillet.
Dredge each piece of chicken in the flour, shaking off any excess. Dip them back into the buttermilk mixture, then back into the flour. Make sure to shake off excess flour or it’ll burn while frying.
Fry 3-4 chicken pieces at a time, occasionally turning them over. Cook for 10-12 minutes, until golden brown, crispy, and the internal temperature reaches 165°F (75°C). Rest the cooked chicken pieces on a wire rack to let excess oil drain off.