01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper or lightly grease it.
02 - Peel onions; slice into ½-inch thick rings and carefully separate them.
03 - Arrange three shallow bowls: mix flour, salt, pepper, and smoked paprika in the first bowl; whisk eggs and milk in the second; combine panko breadcrumbs and Parmesan cheese in the third.
04 - Dredge onion rings in the flour mixture, shaking off excess; dip into egg mixture, letting excess drip; coat thoroughly with panko-Parmesan mixture, pressing gently to adhere.
05 - Place coated onion rings in a single layer on the prepared baking sheet and spray generously with oil.
06 - Bake rings for 10 minutes until golden on the bottom.
07 - Turn the rings over, spray again with oil, then bake for an additional 8 to 10 minutes until crisp and golden.
08 - Serve immediately with your preferred dipping sauce.