Peel the potatoes and slice them thinly. It is important for them to have an even size. Meanwhile, thinly slice the onions into strips.

Heat the oil in a frying pan and fry the potatoes along with the onions. The potatoes should be confit-style, just like the onions. They will be ready when they are almost transparent and start to break apart.

In a clean frying pan with a little hot oil, pour the mixture and let it cook for 3 or 4 minutes. After this time, flip the omelette using a plate.

Let it cook for another 3 or 4 minutes on the other side and remove from the heat. With the help of a plate, flip the omelette again to serve it.