Start by peeling and cutting the onions into medium/small wedges, and then pull apart the wedges that are made of multiple onion layers, so you are left with individual pieces of single layered onion.
Add the milk, eggs, and vinegar to a medium mixing bowl. Mix the ingredients together until smooth.
In another bowl, combine the flour, cornmeal, paprika, cayenne pepper, garlic powder, thyme, black pepper, and salt. Mix well.
Work in batches and coat the onion pieces with the flour and cornmeal mixture. Then, transfer them to the milk and egg batter. Coat them, shake off the excess liquid (important, don't skip this), and transfer them back to the flour mixture – coating them again.
Spray the air fryer with cooking oil (I use olive oil spray). Transfer the onions to the basket in a single layer (air fry in batches if needed). Spray them with cooking oil.
Air fry at 400F (200C) for 10-12 minutes, and flip the onions halfway through ,spraying them with more cooking oil.You may need to air fry them for up to 15 minutes until they are golden brown - it depends on your air fryer.When they are done, remove from the air fryer and serve with your favorite dipping sauce. That’s it!