01 - Cut the onions into 1/2-inch thick rings. Separate into individual rings and set aside.
02 - In a shallow bowl, combine flour, garlic powder, paprika, salt, and black pepper. Mix thoroughly.
03 - In a second bowl, whisk together eggs and buttermilk until fully combined.
04 - Place panko breadcrumbs in a third bowl. Arrange all three bowls in assembly line order: flour mixture, egg wash, then breadcrumbs.
05 - Dredge each onion ring in the flour mixture, shaking off excess. Dip into the egg mixture, then coat thoroughly with panko breadcrumbs, pressing gently to adhere.
06 - Place breaded rings in a single layer in the air fryer basket. Lightly spray with cooking spray.
07 - Cook at 400°F for 10-12 minutes, flipping halfway through cooking time, until golden brown and crispy. Work in batches if needed to avoid overcrowding.
08 - Combine mayonnaise, ketchup, Dijon mustard, lemon juice, smoked paprika, cayenne, salt, and pepper in a small bowl. Mix until smooth and creamy. Refrigerate until serving.
09 - Transfer hot onion rings to a serving platter. Serve immediately with the chilled dipping sauce on the side.