Cut the onion in half and then slice each half as finely as possible, making sure the slices are not attached to each other.
Beat the egg in a large bowl, add the extra virgin olive oil, salt, and freshly ground pepper and combine, then add the onions to the bowl and with your hands mix the onion and the egg, so the onion slices get coated with the egg.
Spread the onion on a large stainless steel baking sheet, so it overlaps as little as possible. Add one tablespoon of the flour to a sieve and sift it all over the onions. Mix them around the sheet with two forks.
In a preheated oven at 400F, bake for about 20 minutes, stir again with tongues or forks, and bake for 15 more minutes or until they are crispy. Take them out and let them cool on the baking sheet.