01 - Slice peeled onions into ½-inch thick rings. Carefully separate into individual rings and discard the small centers. Set aside in a large bowl.
02 - Arrange three shallow bowls in sequence. In the first bowl, combine flour, garlic powder, paprika, salt, and black pepper. In the second bowl, whisk together eggs and buttermilk until fully blended. Place panko breadcrumbs in the third bowl.
03 - Working with one ring at a time, dredge in the flour mixture, shaking off excess. Dip into the egg mixture, allowing excess to drip off. Press firmly into panko breadcrumbs, ensuring complete coverage. Transfer to a clean plate.
04 - Arrange breaded onion rings in a single layer in the air fryer basket, ensuring they do not overlap. Lightly spray with cooking spray. Air fry at 400°F for 10 to 12 minutes, flipping halfway through, until golden brown and crispy. Cook in batches if needed to maintain single layer.
05 - While onion rings cook, combine mayonnaise, ketchup, Dijon mustard, lemon juice, smoked paprika, cayenne pepper, salt, and pepper in a small bowl. Whisk until smooth and creamy. Refrigerate until serving.
06 - Transfer hot onion rings to a serving platter. Serve immediately alongside the chilled dipping sauce for the optimal texture contrast.