Cut 1kg of very fresh, firm white fish fillets, such as mahi-mahi, into ¾in / 2cm cubes, removing any skin and bones.
Squeeze and strain the juice of 500g of lemons and 500g of limes, and pour it over the fish.
Stir in 1 small thinly sliced red onion, 3 medium finely chopped red habanero peppers, ½ cup of chopped cilantro, 1 teaspoon of grated ginger, and a pinch of salt. Refrigerate for about 10 minutes, until the fish turns opaque.
