Soak the sliced onions in buttermilk for at least 30 minutes to tenderize and flavor them.
In a separate bowl, mix the flour, garlic powder, onion powder, paprika, salt, and black pepper.
Preheat the air fryer to 375°F.
Remove the onions from the buttermilk, allowing excess to drip off, and coat them in the flour mixture, shaking off any excess flour.
Spray the air fryer basket with cooking spray.
Place the coated onions in a single layer in the basket, making sure not to overcrowd.
Spray the tops of the onions lightly with cooking spray.
Air fry for 10-12 minutes, shaking the basket halfway through, until the onions are golden brown and crispy.
Serve immediately as a topping for burgers, salads, or as a snack.