Begin by slicing the onions thinly and placing them in a bowl.
Drizzle the olive oil over the onions and toss to coat them evenly.
In a separate bowl, mix together the cornstarch or flour, garlic powder, smoked paprika, salt, and black pepper.
Sprinkle the dry mixture over the oiled onions and toss until they are well coated.
If using, add the grated Parmesan and mix again.
Preheat the air fryer to 375°F (190°C).
Spread the onion mixture in a single layer in the air fryer basket.
Cook for about 10-15 minutes, shaking the basket halfway through, until the onions are golden and crispy.
Once done, remove the crispy onions and let them cool slightly before serving.
