Rinse the okra thoroughly under cold water. Trim the stems and slice the okra into ½-inch rounds. For large okra, consider quartering them lengthwise first. Place the cut okra in a large bowl.
Pour buttermilk over the okra pieces, ensuring they're completely submerged. Let soak for 10 minutes, occasionally stirring to ensure even coating.
In a separate bowl, combine cornmeal, flour, salt, black pepper, garlic powder, and cayenne pepper. Mix thoroughly to distribute the seasonings evenly.
In a large, heavy-bottomed skillet or cast-iron pan, heat vegetable oil to 350°F (175°C). The ideal oil depth is about ½ inch.
Working in small batches (about 1 cup at a time), drain the okra from the buttermilk and toss in the cornmeal mixture. Shake off excess coating and carefully place in the hot oil. Fry for 3-4 minutes, turning occasionally, until golden brown and crispy.
Using a slotted spoon, transfer the fried okra to a plate lined with paper towels. While still hot, sprinkle with a pinch of additional salt if desired. Let cool slightly before serving for maximum crispiness.