Peel and slice the potatoes thinly.
Slice the onion finely.
Heat olive oil in a large skillet over medium heat.
Add the potatoes and onion; cook until soft.
In a bowl, beat the eggs with salt.
Drain excess oil from the potatoes and onions.
Mix the potatoes and onions into the eggs.
Pour the mixture back into the skillet.
Cook on medium-low until the bottom is set.
Flip the tortilla to cook the other side until golden brown.