Prepare the Onion: Cut off the top (pointy end) of the onion and place it cut-side down. Make 4 even cuts down the sides without slicing all the way through. Continue making vertical cuts between each section until you have 12–16 petals. Gently separate the layers to form the bloom.
Soak in Ice Water: Place the onion in a bowl of ice water for 5–10 minutes to help the petals open wider. Drain and pat dry.
Prepare the Coatings: In one bowl, whisk together the flour and spices. In another bowl, mix the eggs and milk.
Coat the Onion: Dip the onion into the flour mixture, making sure to get between the petals. Shake off the excess. Then dip it into the egg mixture and back into the flour for a double coating.
Spray or Brush with Oil: Lightly spray or brush the onion with olive oil to promote crisping.
Air Fry the Onion: Place the onion in the air fryer basket (cut-side up). Cook at 350°F (175°C) for 18–20 minutes, or until golden brown and crispy.
Serve and Enjoy: Carefully remove the onion from the basket. Serve warm with your favorite dipping sauce.