Slice top off onion and trim the bottom (root side) so it will sit flat but don't cut above the root structure.
Sit onion on it's top and slice through roughly 1/4' from root to the top. Do this to create the 'petals'.
Carefully turn upright and place into a container.
Pour buttermilk on top until the onion is covered. Place in fridge for about an hour.
Carefully remove onion from buttermilk and drain saving about 1/2 to 1 cup of the buttermilk.
Add two eggs to the buttermilk and whisk. In a separate bowl mix together flour, paprika, garlic powder and salt.
Pre-heat your air fryer to 390oF
Dip or pour the egg mixture over the onion making sure it gets into all the petals, drain then carefully dip and sprinkle with the flour mixture. Shake/dust the excess flour off the onion then repeat the process by dipping in the egg, then the flour again.
Drizzle or spray all over the onion with oil and ensure the flour is coated, especially near the inside root of the onion.
Carefully place in the basket of your pre-heated Foodi for 10-15 minutes. Check it every few minutes and respray with oil if necessary.
Notes
Next time I make this I'm going to try adding panko crumbs to the flour.
If the onion is browning to fast, turn the temperature down to 360 or 375 to allow the onion to cook longer.