There is an excellent tapas place near the parliament called La Taberna de la Dolores.
If you want to eat really really spectacular baby lamb roasted in wood fire oven try Asador de Aranda near Plaza Callao.
El teletipo bar, calle Garcia Paredes: authentic and varied traditional Spanish food.
If you like seafood and fish go to La Bilbaina in Calle Marques de Urquijo.
Famous ones: Casa Lucio at calle Cava Baja.
29 Fanegas in Calle General Oraa (http://www.tripadvisor.es/Restaurant_Review-g187514-d789250-Reviews-RESTAURANTE_29_FANEGAS-Madrid.html)
If you want to have tapas the Huertas area in the center of town is also a good place.
I cannot say much for new and trendy. Don´t really know any.
Hope u enjoy it about 7 years ago