After seven years living in Barcelona, I'm more than aware of the limited variety of traditional Catalan and Spanish sweets. Most truly traditional recipes (mantecados, roscón) are powder-dry and really must be consumed with coffee or wine, and the rest of the Spanish dessert canon has been imported from other parts of Europe: Crema Catalana is just crème brulée, and brazo gitano (gypsy arm) is really a swiss roll.
No matter, Barcelona is experiencing a dessert renaissance of sorts, and bakeries like Strata are popping up around the city.
Strata specializes in delectable favorites like brownies, black forest cake, apple pies, cheesecake, carrot cake, chocolate chip cookies and even has savory pastries for friends that aren't into sweets. Add to that top-notch coffee and a wide variety of teas available and it's the ideal afternoon delight.
Oh, and Sundays they do a buffet brunch for around 10 euros--hard to beat in the Catalan Capital.