Pat okra slices completely dry with paper towels, then soak in buttermilk for 10 minutes.
In a shallow dish, combine cornmeal, flour, salt, garlic powder, black pepper, and cayenne pepper.
Heat 2 inches of vegetable oil in a large heavy skillet or Dutch oven to 375°F.
Remove okra from buttermilk in small batches, letting excess drip off, then dredge in the cornmeal mixture until well coated.
Carefully add okra to hot oil in batches, being careful not to overcrowd the pan.
Fry for 3-4 minutes until golden brown and crispy, turning occasionally for even cooking.
Remove with a slotted spoon and drain on paper towels.
Season with additional salt if desired and serve hot with ranch dressing or your favorite dipping sauce.