Peel the potatoes and cut them into thin slices, about 1/8 inch thick.
Heat a generous amount of olive oil in a large non-stick skillet over medium heat.
Add the potato slices to the skillet and cook them slowly, stirring occasionally to prevent sticking.
While the potatoes are cooking, thinly slice the onions.
Once the potatoes are golden and tender, remove them from the skillet using a slotted spoon and transfer them to a plate lined with paper towels to drain excess oil.
In the same skillet, add the sliced onions and cook them until they are soft and translucent.
Remove the onions from the skillet and set them aside.
In a large mixing bowl, beat the eggs with a pinch of salt until well combined.
Add the cooked potatoes and onions to the beaten eggs and gently mix everything together.
Heat a smaller non-stick skillet over medium heat and add a tablespoon of olive oil.
Pour the egg, potato, and onion mixture into the skillet, spreading it evenly.
Cook the tortilla for about 4-5 minutes, or until it is set around the edges and the bottom is golden brown.
Carefully flip the tortilla using a large plate or a lid to cover the skillet, and cook for an additional 4-5 minutes on the other side.
Once the tortilla is cooked to your desired level of doneness, remove it from the skillet and let it cool slightly before cutting it into wedges.
Serve the Tortilla Española warm or at room temperature, garnished with a sprinkle of salt and a drizzle of olive oil.