Casa Patas is a well-known and well established restaurant. It also shares the distinction of being a place where you can not only eat good quality, traditional Spanish food, ranging from lamp chops and steaks to salads and beans, but also listen and watch the very best Flamenco shows (its in a side room and you will have to pay for this). Its famous guests include Johnny Depp, Naomi Campbell, Antonio Canales and William Dafoe. Once when I was there, the famous Spanish guitarist Paco de Lucía was seated on the table next to mine – it made my year!
Address: c/ Cañizares, 10. Metro: Tirso de Molina or Antón Martín. A map can be found on their Web site along with a list of upcoming events and menus (all in English!)