Preheat the oven to 180°C / 350°F / Gas mark 4.
Rinse the rice under cold water and drain through a fine sieve.
In a large saucepan, add the brown rice and 650ml water over a high heat.
Bring to the boil, then cover and reduce to the lowest heat possible.
Cook for 35-40 minutes.
Stir to make sure all the water has been absorbed.
Place the tomatoes, olives, garlic, capers and sugar into an ovenproof pan and cook on a simmer for 15 minutes, stirring occasionally.
Place the fish into the pan and spoon over the tomato sauce to make sure the cod is completely covered.
Bring the sauce back to a simmer and then cook for 10-12 minutes, in the oven or until the cod is cooked through and tender.
Serve with the brown rice and scatter the rosemary leaves over the top.
Spoon over any remaining sauce and serve immediately.