Cut off the top portion of the onion and peel back the outer skin.
Flip the onion over and trim off the roots, if needed.
With the bottom side up, cut straight through from top to bottom working around the center of the onion. You should end with approximately 16-20 sections.
Soak onion in ice water while you make up the mixtures.
For the onion breading:
Mix all dry ingredients together in a medium bowl.
In another medium bowl combine the eggs and milk until smooth. Add 1/4 cup of the flour mixture to the milk mixture and whisk until smooth.
On a large plate, place 1 cup panko crumbs and lightly spray with oil of your choice.
Remove onion from the ice water and let it drain for a minute.
Coat the onion in the flour mixture making sure to get flour in between onion petals.
Then soak the onion in the milk mixture, again opening petals to ensure milk gets the flour mixture dry.
Then place onion back into flour bowl and pour panko crumb mixture over the top of the onion, working to get crumbs between each onion petal.
Cook in the air fryer:
Make a foil sling by folding some foil into a somewhat narrow strip and making two handles at the end of the foil.
Place the onion inside the air fryer basket, on top of the foil sling and spray with oil.
Cover with foil, securing two sides under the onion and leaving the other two sides open for air flow.
Air Fry at 370°F/187°C for 15 minutes. Remove the foil and then cook for 3-5 minutes more, depending on the size of your onion and your air fryer wattage. The final result should be nice and toasty with just some light charring on the ends of your onion.
Lift the foil sling handles and place onion on your serving platter and enjoy with dipping sauce.