Peel onions and slice into rounds of 15mm-20mm thick and separate the rings.
Put rings in a bowl and pour over malt vinegar to cover. Leave in the fridge overnight.
Remove the onions from the vinegar. Pat dry to absorb any excess vinegar.
In a mixing bowl sieve rice and self-raising flour. Season with salt and add beer. Whisk any lumps out until the mixture has the consistency of double cream.
In a separate bowl dust the onion rings in a little extra flour to ensure the batter sticks well.
Set the deep fryer to 180°C, or heat oil in a deep pan.
Dredge the onions through the batter mix, letting any excess batter drain off before gently lowering into the hot oil.
Fry the onion rings for 3-4 mins or until the batter is golden brown.
Drain the onion rings on paper towel and season with flakey salt.