From BBC Good Food website: 

Ingredients

  • 3 tbsp olive oil
  • 1 large onion , sliced
  • 2 garlic cloves , sliced
  • 1 red chilli , finely chopped
  • 2 tbsp tomato purée
  • 1kg tomatoes , roughly chopped
  • 200ml white wine
  • 350ml fish stock
  • 3 strips orange zest
  • 1kg skinless halibut fillets, cut into large chunks
  • 500g clams
  • 400g large raw prawns
  • handful flat-leaf parsley , chopped