Best as for me or for someone I do not know personally very well ?
Complicated question as I only know my palate and my family´s.
In Madrid, I would go with Paco Roncero, La Terraza or Fernando Del Cerro, chef and owner of Michelin Casa José or PEDRO LARUMBE who has been in the business since 1970s. His carte is splendid.
Tough call my friend. The best restaurant that I've been to in Madrid was Ramon Freixa. The place I most want to try is Club Allard. Sant Celoni and La Terraza are also wonderful.
What do you mean more casual? If you could specify budget, area, type of food maybe I could make some suggestions.
Ah am going to Ramon Freixa tomorrow! Just had lunch at Sergi Arola was great and might do Sant Celoni on Monday, though I've heard it doesn't quite justify the price tag...any thoughts?
Not fussed about budget or area really, interested in traditional and contemporary Spanish? Is there anything good open on Sunday? Does Fast Good still exist btw?
Ive never been to Sant Celoni myself but Ive heard nothing but praise for it.
Sunday for lunch many places open, dinner is where you'll have difficulty. For lunch, my recommendation would be to go take a nice walk across the beautiful retiro park to the ibiza neighborhood. There you can find the best tapas bars in Madrid. These places do not cater to tourists so if you speak no spanish you may have difficulties:
La Monteria c/ Lope de Rueda 35
La Castela c/ Doctor Castelo 22
Carlos Tartiere c/ Menorca 35
Taberna Laredo c/ Menorca 14
El capricho c/ Doctor Castelo 14
These places fill up fast so I'd recommend arriving earlyish, around 1:00-1:30. If you go to La Monteria off the menu they normally have a fantastic dish of red tuna, worth ordering.
Dinner is much more difficult. Several restaurants I very much like which are off the michelin map, such as Lua, Sacha, Conlaya, and a few more all close on Sundays. I know the Cafe del Oriente is open on sundays, the food is more than decent, the wine list is impressive, and the location is unbeatable.