Heat all but 2 tablespoons of the oil in a large frying pan. Add the potato slices, onion and red and green peppers and cook, stirring lots, for 15 minutes, until all the vegetables are golden and tender.
In a bowl, beat the eggs then stir in the potato mixture from the pan and add a dash of salt and pepper. Put on one side to stand for 15 minutes.
Heat the rest of the oil in a frying pan and tip in the tortilla mixture. Cook over a low heat for 10 minutes, until almost cooked through. Flip over and cook the other side for another 5 minutes, or until the tortilla is cooked on both sides. Leave it to cool then cut into wedges.