Prepare the Onion:

Peel the onion and cut off the top (stem end), leaving the root intact.

Place the onion root-side down and make 8–12 evenly spaced cuts from the top down to the root, creating "petals." Be careful not to cut through the root. Gently separate the petals to create the blooming effect.

Make the Dipping Sauce:

In a small bowl, mix the mayonnaise, ketchup, horseradish, paprika, garlic powder, salt, and pepper. Cover and refrigerate until ready to serve.

Season the Flour:

In a mixing bowl, combine the flour, paprika, garlic powder, onion powder, salt, and black pepper.

Coat the Onion:

In a separate bowl, whisk together the eggs and milk.

Place the onion in the flour mixture, coating all the petals. Shake off excess.

Dip the onion into the egg mixture, ensuring it's fully covered, then back into the flour mixture. For extra crunch, coat the onion in panko breadcrumbs after the second flour dip.

Preheat the Air Fryer:

Preheat your air fryer to 375°F (190°C) for 3–5 minutes.

Air Fry the Onion:

Spray the onion generously with cooking spray to help it crisp up.

Place the onion in the air fryer basket root-side down. Cook at 375°F (190°C) for 15–20 minutes, checking and spraying with cooking spray halfway through, until golden brown and crispy.

Serve:

Remove the blooming onion from the air fryer and serve immediately with the dipping sauce on the side.