Run to this little gem of a tapas bar on Ortega y Gasset near Serrano in barrio Salamanca. I just got back from a few tapas for dinner with some friends from Madrid and we ordered the Milhojas de Ventresca. I have to say that this is one of the best dishes I have had this year. I thought it would be tuna wrapped with milhojas, but instead it was a layer of ventresa (tuna), roasted peppers, homemade mayonaise and a few raw onions on top. The plate was rather large and was adorned with a very light basil sauce. The mixture of flavors was outstanding, especially since they gave us bread to soak up the sauces.
We also shared a sabrosada con brie, which was a bit too heavy for my taste, and a cabrales spread with duck ham over toasted bread. There's a restaurant in the back too, but we just sat in the front. Apparently the owners are a little strange according to my friends, but people deal with them because the food is delicious.