Tortilla de Patatas

Peel and slice the potatoes into thin rounds, and finely slice the onion.
Heat the olive oil in a large skillet over medium-high heat. Add the sliced potatoes and chopped onions to the skillet, season with salt and pepper, and cook for about 10-12 minutes until the potatoes are tender, stirring occasionally.
In a separate bowl, beat the eggs together with a pinch of salt and pepper.
Once the potatoes and onions are cooked, remove them from the skillet with a slotted spoon, and drain off any excess oil.
Add the potatoes and onions to the beaten eggs, and mix well.
Heat a non-stick skillet over medium heat, and add the potato and egg mixture to the skillet. Spread the mixture evenly in the skillet, and cook for about 5-7 minutes on one side until the bottom is golden brown.
To flip the tortilla, place a plate over the skillet and carefully invert the tortilla onto the plate. Slide the tortilla back into the skillet, uncooked side down, and continue cooking for another 5-7 minutes until the other side is golden brown.
Once the tortilla is cooked through, remove it from the skillet and let it cool for a few minutes. Cut the tortilla into wedges and serve warm or at room temperature.