Heat the oil in a saucepan over a medium heat, then add the onion and fry gently for about 5 minutes until softened and beginning to colour.
Add the garlic and chilli and fry for a couple of minutes more, then add the tomatoes, tomato puree, sugar and half the basil.Bring to a simmer and cook for about 20 minutes until thickened and reduced. Season to taste.
Meanwhile, cook the pasta according to packet instrctions, then drain.
Just before serving add the mozzarella to the sauce, then stir into the pasta.Divide between two pasta bowls and sprinkle with the remaining basil and some grated parmesan