Method

1. Boil the spaghetti according to the packet instructions in plenty of boiling salted water.

2. Drain the spaghetti and reserve about a tablespoon of the cooking water.

3. Meanwhile, gently sauté the onion in the butter until softened.

4. Add the tomatoes and the olive oil and cook briefly.

5. Mix together the tomato sauce and the reserved pasta water.

6. Add the parsley and seasoning. Add sauce to the spaghetti and mix thoroughly.

7. Serve hot.