A cataplana is a copper pan made of two clam shells that can be sealed with a clamp. The origins of this cooking contraption are lost in time. In the early 20th centuries Portuguese hunters carried cataplanas loaded with onions and tomatoes, so they could cook game on a wood fire. Later, in the 1960s, the cataplana became a popular way to cook fish and shellfish in the Algarve. Since then, it has become a hallmark of Portuguese cooking. There is something magical about the moment when the waiter brings a cataplana to the table. And it is not hard to imagine that, as he opens the pan, he murmurs the same secret incantation used in the banquets of the Arabian Nights to make the meal unforgettable. Taken from http://saltofportugal.