Tortilla de patatas (potato omelette) is also sometimes called Tortilla española de patatas (Spanish omelette) to differentiate it from the dish commonly known as tortilla francesa (French omelette) or just tortilla, which is made only with eggs. It is a very popular dish at any kind of event in Spain and can be served either cold or hot. It is also served as a tapas dish. Although potatoes and eggs are the basic and in most cases the only ingredients of a tortilla de patatas, is very common to find it with onion.