I too agree with richardmadrid and pim. To have tapas in the Plaza Mayor Madrid you're paying and should expect to pay for the quality of location and view than for the quality of tapas. Really, to me, the tapas in the Plaza Mayor are average in quality so for me, "average" is just fine if the setting is special. I honestly don't mind paying 3-4 Euros for a coffee with milk or the same for a pincho of tortilla de patatas if I can sit at a table IN the Plaza Mayor or in an old bar/restaurant in the gallery of same.
Between Plaza Mayor and Puerta del Sol there are MANY tapas places. While not "pretty" or "historic-looking" at all, I like the "LAS BRAVAS" chain of tapas places. These places are POPULAR more with the local madrileños - they're cheaper (the place, not the madrileños), they're busier, and to me they're better. Oh, they're usually HOTTER too. You'll find several threads about tapas as well as a nice, LONG thread in this forum about the "LAS BRAVAS" chain entitled "
Patatas Bravas in Madrid by using the SEARCH link above/right on all pages.
But really, for me, I love to finish an evening with a coffee Madrid's Plaza Mayor under the stars.
Have a great time in Spain! Saludos, MadridMan