Preheat the oven to 200ºC/400°F/Gas 6
Heat oil in a saucepan and add the onion and garlic (if using). Cook until softened.
Add the tuna and heat through and mix up for a minute or two.
Add the tin of chopped tomatoes,mixed herbs, sweetcorn and cook for about 10 minutes.
Meanwhile cook the pasta according to the packet instructions.
Once the pasta has cooked, drain and add to the tuna mixture.
Transfer to an oven dish, top with grated cheese and bake until cheese is golden and bubbling.