Bacalao is Spanish for cod fish. Salt cod is a staple of the Spanish diet, even though refrigeration has eliminated the need to salt fish to preserve it. Salt cod is especially popular in central and northern Spain and is often served in Spanish homes and restaurants, especially during Lent and Christmas.
There's no doubt about it, the tortilla española or Spanish omelet is the most commonly served dish in Spain. In a country filled with regional food, some might call it the national dish. In Spain, it's usually called tortilla de patata or potato omelet.