I finally had the opportunity to go to one of the most traditional restaurants in Madrid. It is one of the places I had never been too despite living here. The restaurant is quite affordable (a set meal for some 20€ very nourishing).
It is located right in the center of Madrid, in La Bola street, more precisely. And it is a a magnificent restaurant. A unique place where you can enjoy in a very special way the most relevant traditional dish in Madrid: the cocido (stew with various types of meat, vegetables, potato, legumes... typical in Madrid).
It is a restaurant where the familiar aspect has been preserved. We could even go into the kitchen to see how they make, all week long, the delicious dish, in the most traditional way as they can.