Heat the oil in a large non-stick pan over a medium heat. Add the onions and fry for 5-8 mins until starting to colour. Add the courgette, garlic and chilli flakes, if using, and cook for a further 3-5 mins until the courgette starts to go very soft.

Stir in the tomatoes, a can full of water, tomato purée, the vinegar, bouillon, olives and capers, bring to a gentle simmer and cook, uncovered, for 15 mins.

Meanwhile, bring a large pan of salted water to the boil. Cook the spaghetti following pack instructions, then drain and toss with the sauce and parsley. If you're following the Healthy Diet Plan, serve two portions with half the cheese scattered on top, and chill the rest for another day. Will keep chilled for up to three days. Reheat portions in the microwave until piping hot, or on the hob, covered, over a medium heat with a splash of water to loosen.