Bring a big pot of salted water to the boil and cook spaghetti according to packet instructions.
Cook the onion in a frying pan over medium heat until soft and translucent. Add the garlic and cook for another minute.
Add the tomatoes and cook, stirring every now and then for five minutes.
Drain the pasta and at the last minute, add the prawns to the frying pan, tossing so completely warmed through.
Tip the pasta into the frying pan, add the Paul Newman’s Own Balsamic Dressing and a sprinkling of chilli flakes and toss to combine. Serve immediately.