1 large onion, peeled and thinly sliced

1kg of 3cm thick halibut fillet

450ml natural yoghurt

Juice of half a lemon

1 tsp sugar

1 tsp salt

¼ tsp freshly ground black pepper

¼ tsp garam masala

2 tsp ground cumin

2 tbsp ground coriander seeds

½ tsp cayenne pepper

1 tsp freshly grated ginger

3 tbsp vegetable oil

50g unsalted cold butter cut up into small chunks

• Pre-eat the oven to 190°C / gas mark 5.

• Lay the onions on the bottom of a large based baking dish, one that is big enough to lay the fish flat in one layer.

• Cut the fish into four equal sized portions and place on the onions.

• Mix the Yoghurt with the lemon juice, salt, pepper, garam masala, cumin, coriander, cayenne, ginger and oil, mixing well.

• Pour the sauce onto the fish, making sure that some of it goes under as well as over.

• Cover with either a lid or foil and bake in the oven for approximately 30 minutes, or until the fish is cooked.

• Pour off the sauce from the fish into a saucepan and boil to reduce to about 350ml of liquid.

• Whisk in the butter, and as soon as it is melted, pour over the fish and serve