Bring a large pot of water to the boil and cook the pasta for 1 minute less than recommended on the pack. Drain.
Whilst the pasta is cooking, heat the oil on a medium heat in a large frying pan. Add the onion and cook for 3-4 minutes until softened.
Add the peppers, salt, pepper, garlic, tomato puree and basil. Stir and cook for 2-3 minutes.
Add the tinned tomatoes and cream, bring to a gentle bubble and add the pasta and lemon. Stir everything together and add the tuna gently. Transfer everything to a large baking dish.
Top with cheddar and place in the oven for 15-20 minutes, until the cheese is golden brown.