Step 1: Prepare the Onion

1. Cut off ½ inch from the pointy end of the onion (not the root) and peel off the outer skin.
2. Place the onion root-side down on a cutting board. Using a sharp knife, make 16–20 cuts from the top of the onion down to the root, spacing them evenly to create petals. Be careful not to cut through the root.
3. Gently separate the onion layers to “bloom” the petals, taking care not to break them.

Step 2: Make the Batter and Coating

1. In a large mixing bowl, combine the flour, paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper.
2. In a separate bowl, whisk together the eggs and milk to create the wet batter.

Step 3: Coat the Onion

1. Place the onion in the flour mixture, ensuring the flour gets into all the layers. Shake off any excess.
2. Dip the onion into the egg mixture, coating it thoroughly.
3. Return the onion to the flour mixture for a second coating, making sure every petal is covered.

Step 4: Heat the Oil

1. In a deep fryer or large heavy-bottomed pot, heat the vegetable oil to 375°F (190°C). Ensure there is enough oil to fully submerge the onion.

Step 5: Fry the Onion

1. Carefully lower the coated onion into the hot oil, root-side up, using a slotted spoon or spider strainer. Fry for 7–10 minutes, or until golden brown and crispy.
2. Remove the onion from the oil and drain on a plate lined with paper towels.

Step 6: Make the Dipping Sauce

1. In a small bowl, mix together the mayonnaise, ketchup, horseradish, paprika, garlic powder, onion powder, cayenne pepper, salt, and pepper. Adjust seasonings to taste.

Step 7: Serve and Enjoy

1. Place the blooming onion on a serving platter and serve warm with the dipping sauce in the center or on the side.