Sorry I didn´t get back to you earlier, but....
First af all, in Madrid, there are restaurants and tapas bars, practically everywhere, so, is very easy to find places to enjoy. I can give you a few pointers on places with a certain reputation of quality, that also mean higher prices.
In the Moncloa-Argüelles area there is Dominus in calle Francisco de Ricci, 15. I haven´t been there in the last year but used to be quite good.
In calle Ferraz, 36, there is el Antojo. Very good , with a well known cook. Expensive though. In Paseo de Rosales there are a few that are OK. Casa de Levante, I´m not sure is still open, I heard had closed recently, also towards the parque del Oeste there is el Molino de los Porches, Pintor Rosales, 1. On the gardens side of the street. It shouldn´t be difficult to locate because it looks like a country house. In Vallehermoso, 94, almost corner with Cea Bermudez, los Asturianos, good healthy food.
As far as the Plaza mayor area, there are tons of restaurants (turistic), here are a few that are good.
In addition to Botin and in the calle Cava Baja you can find Lucio (castillian), la Posada de la Villa (castillian), Julian de Tolosa (vasque).
In th parallel street, Cava Alta, 32, is las Isidras (madrileñan). Also of the same type there are Rest. Malacatin (Ruda,5), el Villagodio (San Agustin, 6),Genoveva de Barri (Espejo, 10), Casa Ciriaco (Calle mayor, 84).
A little farther, towards calle Atocha and Plaza Anton Martin, el Ventorrillo Murciano, in Tres Peces, 20, (very good for rices and fresh vegetables from the S.E. area of Spain) and, finally, towards the Gran Via area, a nice place for tapas and meals is la Tasquita de Enfrente, Ballesta, 6.
If you want to explore a little more you can go to
www.paginasamarillas.es, go to restaurants and you can get more info.
I hope you know some spanish!!!!