Midrange
El Aljibe
In the Havana suburb of Miramar, El Aljibe is the definitive proof that food in Cuba needn't be bland. Try the house specialty, chicken in sour orange sauce. El Aljibe also has a remarkably well-stocked wine cellar.
La Casa
This stylish restaurant, located in Nuevo Vedado, is a large California-style house typical of the 1950s. The dining room and garden are inviting and intimate. The impeccable service and consistency uncommon in Cuba, are a must in Havana. Website adress: Restaurant La Casa
There are many good, mid-priced restaurants in Chinatown. "Bavaria" is one of the best if you can picture a restaurant named after a German province pronounced like "barbaria" with Chinese decor, serving pizzas and spaghetti.
Whilst Convertible Peso restaurants can be quite expensive at the top end for rather mediocre food, some such as the Café de Oriente have a splendid ambiance. The average government-run restaurants are about US$20 for two.
breakfast
All the tourist hotels serve breakfast, typically a buffet with a wide variety of good food, although overpriced 15 CUC at the Hotel Nacional. If you stay in a casa particular ask whether you'll be served breakfast. If not, ask the landlord/lady to take you shopping. Otherwise, there's almost no hope of finding a restaurant open for breakfast. One exception is the Chan Li Po Bar-Cafeteria, open at 9AM, in Centro Habana, near Chinatown, at Perseverancia #453 between Zanja and San Martin.
Budget
Peso stalls are all over the city, particulary on Prado Marti.
Some restaurants like Hanoi, in Calle Brasil, offer generous meals for 5CUC.
With Cuban national pesos, you can get ice cream for only 1 peso US$0.04 in small street booths scattered around the city. You can also get a filling bocadito small ham sandwiches or a cajita small meal in a cardboard box for less than 20 pesos US$0.80, or a "pizza" for 7-10 pesos US$0.40.
Particularly, the Terminal de Omnibus, by the Plaza de la Revolucion, has a very good peso cafe with offerings as fried chicken for only 25 pesos $1.00 USD.