The dish is named after the hinged copper pan it's cooked in, not the food itself — the pan's clamshell shape traps steam so tightly that everything inside essentially cooks itself.
Clams, shrimp, fish and sausage are layered with tomato, onion, garlic and peppers inside a sealed copper cataplana pot and steamed together until the flavors meld. Beachside stalls and market seafood counters across the Algarve serve it straight from the pan.