Pat okra completely dry with paper towels; soak in buttermilk 10 minutes.
Mix cornmeal, flour, salt, garlic powder, pepper, and cayenne in a shallow dish.
Heat 2 inches oil in a large heavy skillet or Dutch oven to 375°F.
Drain small batches of okra, letting excess buttermilk drip off; dredge thoroughly in cornmeal mixture.
Carefully add to hot oil in batches without crowding.
Fry 3-4 minutes until golden brown and crisp, turning occasionally.
Remove with a slotted spoon; drain on paper towels.
Add salt if desired; serve hot with ranch or dipping sauce.