Prep time: 13-15 minutes
Cooking time: 26-30 minutes
Preheat the oven to 1900C / 1700Fan / Gas Mark 5.
Heat 2 tbsp olive oil in a frying pan over a medium heat. Saute the red onions, tomatoes and garlic for 2-3 minutes until the tomatoes have softened.
Pour into an oven proof dish, season and place the smoked haddock fillets on top.
Tear the mozzarella evenly over the smoked haddock and sprinkle with the cheddar cheese.
Place the rosemary sprigs on top and drizzle with the remaining olive oil.
Place on a baking tray and bake in the oven for 20 minutes until golden brown.
Serve with chunks of crusty white bread.