Peel and chop the potatoes and the onion. Heat oil in a pan—it should be hot but not smoking—then add the onion. Let it cook for a moment.

Add the potatoes, stir, and reduce the heat to very low. Cover the pan. Stir occasionally and add a little salt. If it starts frying too much, lower the heat even more.

Let it cook for about 20 minutes. Meanwhile, beat the eggs with a pinch of salt on each egg.

Drain the potatoes and onions using a colander, collecting the oil in a bowl underneath. Immediately add the potatoes and onions to the beaten eggs, and drizzle a little oil into the mixture. Stir well so the egg mixes thoroughly with the potatoes. Let it rest for a minute.

The mixture will thicken as the egg sets a bit. In the same pan, add a little oil and heat gently, then pour in the mixture. Lower the heat to the minimum.

Spread the mixture evenly and use a spatula to loosen the edges. Move the pan to check if the omelette is loose. Place a plate or lid over the pan and flip the omelette. Press down gently to spread the potatoes. Cook for another minute, flip again, and cook for another minute. If you like it well done, flip once more. And it's ready—enjoy!