Peel and slice the potatoes thinly.

Heat olive oil in a large skillet over medium heat.

Add the potatoes and cook until tender, about 10-15 minutes.

If using, add the sliced onion and cook until soft.

Drain excess oil from the potatoes and cool slightly.

In a bowl, beat the eggs and season with salt.

Combine the potatoes with the beaten eggs, mixing gently.

Wipe the skillet and add a bit more oil, heating it over medium heat.

Pour the potato and egg mixture into the skillet, spreading it evenly.

Cook for about 5-7 minutes, then flip the tortilla and cook the other side for another 5-7 minutes.