01 - Cut onions into ½-inch thick rings. Separate into individual rings and set aside.
02 - Combine flour, garlic powder, paprika, salt, and black pepper in a shallow bowl.
03 - Whisk together eggs and buttermilk in a second shallow bowl.
04 - Place panko breadcrumbs in a third shallow bowl.
05 - Dredge each onion ring in flour mixture, dip into egg wash, then coat thoroughly with panko breadcrumbs.
06 - Place breaded rings in a single layer in air fryer basket. Lightly spray with cooking spray.
07 - Cook at 400°F for 10-12 minutes, flipping halfway through, until golden brown and crisp. Work in batches if needed.
08 - Mix mayonnaise, ketchup, Dijon mustard, lemon juice, smoked paprika, cayenne, salt, and pepper until smooth. Refrigerate until serving.
09 - Serve crispy onion rings hot with dipping sauce on the side.