Caldou (Casamance fish in lemon broth)

Light, tangy and clean-tasting, caldou is the fish dish of Ziguinchor and the river towns of Casamance, where fresh catches from the estuary are poached in a broth sharp with lemon, sweet with soft onion and tomato, and warmed by a whole chilli. It is ladled over plain white rice so the grains soak up the broth, with an extra squeeze of lemon at the table. Some cooks add a few okra or a spoon of palm oil; this version keeps it simple and light. Firm white fish such as grouper, sea bream or hake is ideal. Chef's tip: keep the broth at a bare simmer once the fish goes in; boiling it hard is the common mistake and turns delicate fish dry and broken.