Put a pot of salted water on for the pasta. Remove the sausages from their skins.
Heat the oil over a medium heat and add the onion and pepper and cook until softened. Brown the sausage in the pan with the veggies, breaking up with a wooden spoon. Add the garlic, oregano, balsamic and tomato puree and cook for another couple of minutes then pour in the chopped tomatoes, add the sugar and bring to a simmer. Cook for about 10 minutes.
While the sauce cooks add the pasta to the boiling water and cook according to packet instructions.
Remove a mugful of pasta cooking water. When the pasta is cooked to al dente drain and add it to the sauce along with a mugful of pasta water and toss together. Serve with grated parmesan.
Notes
Nutrition information is an estimate and will vary depending on the exact ingredients used.