Heat olive oil in a large non-stick frying pan over medium heat. Add the potatoes and onions, and cook gently until the potatoes are tender and slightly golden. Stir occasionally to prevent sticking. This process will take about 15 minutes. Remove from heat and set aside.
In a large bowl, crack the eggs and beat them lightly with a fork. Add a pinch of salt and mix well.
Add the cooked potatoes and onions to the bowl with the beaten eggs. Gently fold the mixture together until all the ingredients are evenly coated.
Place the frying pan back on the heat and add a little more olive oil if needed. Pour the potato and egg mixture into the pan, spreading it out evenly.
Cook the tortilla over low heat for about 5-7 minutes, or until the edges are set and the center is still slightly runny.
Carefully flip the tortilla using a flat plate or a lid that is larger than the frying pan. Slide the tortilla back into the pan, uncooked side down.
Continue cooking for another 5 minutes, or until the center is fully set and the tortilla is golden brown on both sides.
Once cooked, remove the tortilla from the pan and let it cool for a few minutes. Cut it into wedges or squares.
Once cooked, remove the tortilla from the pan and let it cool for a few minutes.
