Every winter there is a tradition of a particular meal that can be eaten in Barcelona and sorrouding areas : it is called "Calçots".
The Calçots are kind of a large onion (30 cm/10 inch) that gets grilled and stored wrapped in newspapers to keep them warm. To eat them you have to peel the black grilled skin with your hands and deep the onion in a delicious sauce called "Romesco". Looks strange the first time but is absolutely a must do experience extremely well appreciated by locals.
It you ever come to Barcelona around February, you have to definitely taste them. Although you can eat them in Barcelona, the best experience is to leave the city for a daytrip somewhere (for example Montserrat) and have lunch in a restaurant in the countryside to enjoy this experience as a local.