Tortilla
Spanish omelette

Perhaps the most emblematic and versatile Spanish tapa of all, the tortilla can be eaten at any time of day from breakfast to supper and prepared in a multitude of different ways.
Debates range about whether onion should be included or not, but the key to taste is the consistency of the potatoes and egg (slightly runny is favoured by many).
Tortilla paisana is a variation that includes chorizo, red pepper and peas.