Preheat oven to 220C 425F Gas Mark 7
Cut the aubergine into slices (approx. 1.5cm thick) and brush both sides with olive oil.
Place on a baking tray and bake for approx. 8-10 mins (turning once)
Meanwhile fry the onions in the remaining oil for 2 mins. Add the garlic and cook for another min.
Add the peppers and cook until soft.
Add the tuna, passata and tomato puree and simmer for 5 min.
Remove the aubergine from the oven and top with the tuna, tomato topping.
Sprinkle cheese on top and heat for another 5 mins (until the cheese has melted)