Peel and slice a large onion into thick rings. Separate the rings, discarding the smaller ones.
In a bowl, mix all-purpose flour, baking powder, salt, black pepper, and garlic powder.
Add buttermilk and egg to a small bowl, stir until you have a smooth batter.
Dip each onion ring into the batter, making sure it’s evenly coated. Then, roll the battered onion ring in breadcrumbs for an extra crispy finish.
Preheat the air fryer to 375°F (190°C) for about 5 minutes. Place the coated onion rings in a single layer in the air fryer basket. Set cook time for 8-10 minutes, flipping halfway through, until golden brown and crispy. Remove the onion rings from the air fryer, serve hot, and enjoy with your favorite dipping sauce!