Peel the onions and slice them in half, leaving the root intact. Use a mandoline to cut the onions into 1/8'' slices. Place the onion slices into a shallow bowl.

Pour the buttermilk over the top of the onions. Use tongs to make sure the onions are covered by the buttermilk as much as possible. Marinate the onions for at least 15 minutes, but preferably 1 hour. Stir the onions every once in a while to make sure they all get marinated.

While the onions marinate, whisk the flour, garlic powder, onion powder, paprika, cayenne, salt, and pepper in a shallow bowl.

Pour the oil into a 12'' skillet or heavy-bottom pot. Heat the oil over medium until it reaches 350-375°F. Then, place a few paper towels on a large plate and set aside.

Once the oil is hot, use tongs to grab a handful of onions from the buttermilk, letting the excess drip off. Dredge the onions in the flour mixture, tapping off any extra flour.

Carefully transfer the onions into the hot oil. Fry for 2-3 minutes until the onions are golden-brown. While the onions cook, use tongs to occasionally stir the onions and break them apart.

Once the onions are golden-brown, transfer them to the paper towel-lined plate. Sprinkle them with Kosher salt, to taste. Repeat with the remaining onions. Enjoy them immediately as an appetizer or use them on sandwiches, salads, and more!