In a shallow dish combine flour, ¼ teaspoon salt, and paprika.
Whisk egg and water in a separate bowl.
Combine panko crumbs with ¼ teaspoon salt.
Slice onion into ½ inch rings.
Coat onion ring in flour mixture followed by the egg mixture, shaking off the excess between steps. Then press into panko crumbs.
Place on air fryer basket and coat with cooking spray. Air fry at 375 for 7-9 minutes, or until golden brown. Add additional time if needed, starting with 1-2 minutes at a time.