RS Spain, page 504.
When do they open, please? Maceira opens at 13:00, but how about the others?
What if we decide to eat lunch at noon?
Most open between Noon and 1:00, Google will list the specific time, though, in my experience, they will not be ready to serve you at right at opening. As for lunch, I would encourage you to do the local thing, eat a little later, Lunch is not really available before 1:00, 2:00 is more the peak.
The same with an evening meal, aside from bars and tapas places, most more formal restaurants do not even open before 8:00.
That is a very good area for "menu del dia", Terramundi for example. Do you know what "menu del dia" is?
do you know Spaniards do not eat tapas at lunch time during the week but do "menu del dia" instead?
Madridman
I have no idea about "menu del dia".
My goal is to get some food for lunch in Prado area.
Arborvitae- The Menu del Dia is a fixed-price 2-3 course meal, and probably the most common way to eat out for lunch in Spain. Everywhere from neighborhood bars/cafes to nicer restaurants will offer one. It's generally a relaxed, civilized, full meal.
For 12-17€ you'll have a choice of starter and main (usually 3-4 options—fewer than the restaurants' total offering), then you usually have a choice of drink (beer, wine, water), and a choice between dessert or coffee to end the meal. The exact combination may vary, but that's the most common formula. Some places may have different offerings at different price points—a 12€ menu and one for 16€ Of course, you could choose to include dessert and add a coffee. Or include water and order a whole bottle of wine extra.
Many places will have something like a chalkboard or the like at the door, listing the day's offerings.
Excellent explanation from Scudder. Menu del dia is the way Spanish people have lunch in restaurants. It is also the way to tell who is a tourist ;-)
And do you know the best part?, there are plenty of blogs about it:
https://www.walksofspain.com/10-best-restaurants-madrid-lunch-less-15-euros/
https://www.ft.com/content/c6f6f95c-260a-4103-bf9c-a03ca6c0007d
https://www.gastroactitud.com/pista/algunos-de-los-mejores-menus-del-dia-de-madrid/