Pre heat your oven to 230C / 450F
You need to get all your elements prepared in advance and set up a small production line. Things can get quite messy, so keep things close together.
Mix the dusting ingredients and put in a bowl.
Mix the the batter ingredients together with a whisk, it should be the consistency of pancake batter or thick cream, and set aside in another bowl.
Spread the crumb out on a flattish plate / tray.
Line a couple of large baking trays with silicone baking paper. Nothing, and I mean nothing sticks to this. Or use baking paper – in which case spray the sheets lightly with olive oil cooking spray, or brush lightly with oil to prevent sticking.
Now toss your onion rings in the seasoned flour, dip quickly into the batter, shaking off any excess and roll quickly in the crumbs to coat. Place them on the baking tray keeping them separate.
Bake for 10 minutes until they are golden brown.