Probably JUANALALOCA(Plaza Puerta de Moros 4, 28005 Madrid/phone +34 91 364 0525) is one of the best place in Madrid for pintxos inspired by the Basque region. Fusion style, quite sophisticated, unusual and gorgeous. Maybe more expensive than other places but it really worth it. Place is always crowded with food lovers. They are delightful.
salmon with dill, melts in your mouth!
tortilla de patatas(Spanish omelet); it's made with caramelized onions and is sweeter and juicier than the ones you might find elsewhere). Very special!