Method
Heat the oil in a high-sided saute pan over a medium-low heat. Add the onion along with a generous pinch of salt and fry for 10 mins, or until soft. Add the garlic and chilli flakes, and cook for another minute.
Add the tomatoes, anchovies, olives and capers into the onion, bring to a gentle simmer and cook, uncovered, for 15 mins. Season to taste.
Meanwhile, bring a large pot of salted water to a boil. Cook the spaghetti following package instructions, then drain and toss with the sauce to coat well. Garnish with parsley and parmesan.