Basic tomato and basil sauce for pasta

Name: Tomato pasta sauce
Ingredients: 3 tbsp extra virgin olive oil; 1 large onion, chopped; 2 garlic cloves, crushed; 3 x 400g tins chopped tomatoes; ¼–½ tsp dried red chilli flakes; 2 tsp balsamic vinegar; 2 tsp sugar; 1 large handful fresh basil leaves, torn into small pieces; salt and freshly ground black pepper; grated Parmesan, to serve (optional)