Cut the top of the onion off (not the root side). Peel onion and place cut side down. Make 4 downward even cuts around the root of the onion (starting approx. 1/2 inch from the root). Be careful not to cut all the way through. Then go back around and make 3 additional cuts between each quarter.
Turn the onion over and carefully separate the layers into onion petals with your fingers.
Place the cheese slices on top of each other and cut them into 1/2 inch slices. Then cut them in half. Carefully place each slice of cheese in between each onion petal. Then place the onion on a plate and put in the freeze for 45 minutes.
In a mixing bowl, whisk together milk and eggs.
In another mixing bowl, whisk together flour, salt and pepper mixture, and paprika.
Turn on your Ninja Foodi and set to Air Fryer for 330ยบ so Air Fryer can heat up.
Remove the onion from the freezer and place the onion in the flour mixture. Carefully separate the metals and sprinkle flour inside each onion petal. Adjust the cheese as needed. Then use a spatula and dip the onion (root side down and petals facing up) into the wet mixture. Make sure each petal is coated. Adjust the cheese as needed.
Put the onion on a large plate and then sprinkle flour all over the onion. Shake the onion to remove excess flour (adjust cheese as needed). If there are any wet spots, sprinkle more flour. If there are any uncoated spots, use your finger to apply the wet mixture to that spot only, and then sprinkle with flour.
Pick up the onion with both hands and cup the onion by holding the root with your fingers and gently shake over the plate to remove any excess flour. Then place on a dry plate. From a distant, spray the onion with cooking spray so the flour doesn't fall off.
Place onion in the air fryer with a spatula. Air Fry for approx.12 minutes or until the onion is crispy and browned.
Serve the cheesy stuffed blooming onion with a horseradish dipping sauce