Start by mixing all the ingredients for the marinade in a bowl. Dip in the onion slices and leave for 20 minutes. This step is not mandatory but I recommend it.
Put the flour in a bowl.
In another bowl, mix the chickpea flour, corn flour, salt and water.
Put the breadcrumbs in another bowl.
Dip your slices in flour, then in the chickpea mixture and finally in the breadcrumbs.
Bake in preheated oven at 200C for 30 minutes. In the middle of the time, turn your "burgers".
Take out and prepare your burger as you wish.