1. preheat the oven to 400 degrees. spray two large rimmed baking sheets with nonstick spray.

2. place the flour, salt, paprika, pepper, and cayenne in a large zip-close plastic bag. Place the breadcrumbs in a shallow dish. place the egg whites in another shallow dish.

3. Place the onion rings, a few at a time, in the flour mixture and shake to coat. dip each ring into the egg whites, then coat with the bread crumbs. arrange the rings in a single layer on the baking sheets (reserving for another use any broken or small inner rings) and lightly spray the tops with nonstick spray. discard the excess flour mixture, egg white, and bread crumbs.

4. bake until the bottoms of the onion rings are browned, about 10 minutes. turn the rings and bake until browned, about 5 minutes.