Place the potato and onion in a large heat-proof bowl and pour over the olive oil.

Microwave for 10 minutes.

Take the bowl out of the microwave and give everything a stir/turning using a fork. Don't worry if any of the potatoes break up.

Microwave again for 5-10 minutes or until all the potatoes are soft.

Heat a 25cm, non-stick frying pan over medium heat.

Add the potatoes and onions and cook for a couple of minutes, stirring/turning, until they have a little colour.

Spread the potatoes and onions out so they're covering the bottom of the frying pan evenly then pour the egg mixture over the top.

Sprinkle a little salt and pepper over the top.

Cook for about 5 minutes and tip the pan a little so that the egg is evenly distributed.

When it is just set on top there are two options.

The first option is to slide it onto a plate, cover it with the frying pan and then flip it back into the pan (so you're turning it over) then cook for a few more minutes

The other option is to place the pan under a hot grill until it is set (make sure your pan can go in the oven).

Serve the tortila cold or warm.