We asked for recommendations for Madrid restaurants and got feedback from people that lived there for several years. It’s encouraging to note that they concurred on the following 3 restaurants.
If you’re turning up in anything less than a jacket you need to check dress code (many ask for a tie). Madrid tends to be dressier than Barcelona, and the last thing you want is to be turned away at the door or worse, obliged to wear their house jacket/tie outfit! (I’ve kept this to ‘dress code for males’ because dress code for women is so subjective.)
By Plaza Major is Casa Botin. Highly regarded by the locals it is very well known for its Cochinillo (Roast Suckling Baby Pig) which when cooked right, can be carved using a dinner plate. Also good is their Cordero Asado (Roast Lamb).
Also by Plaza Major is Casa Paco, known for their meat and specially their steaks. Their wine list is substantial and decent.
For fish the place we were recommended is La Trainera in the upmarket residential area of Salamanca. Curiously it is accepted that the best fresh fish in Spain is found in Madrid, which is pretty much in the centre of the country but this is where supply and demand come into play. The fish is air freighted in from the coasts so is extraordinarily fresh and the Madrileños are great cooks.
Other specialities are Callos a la Madrileña, slightly spicey tripe, which when done well is sticky and delicious with fresh bread. And Madrid is also known for their Bocadillo de Calamares (squid sandwich) which for some reason usually provokes a smile!