Boil your spaghetti according to the packet instructions. Make sure to reserve about a mug of pasta water.
Begin by finely chopping the anchovies and using the side of your knife to smush them into a paste. Set aside and then roughly chop your kalamata olives and capers!
In a large pan, heat up the extra virgin olive oil on a medium heat. Add in the chopped onion, garlic and anchovies. Fry for 2-3 minutes.
Add in the olives, capers and tomato purée. Fry for a further 3-4 minutes, stirring well throughout.
Pour in your tin tomatoes and rinse the can out with around 4 tablespoons of water. Add in the chilli flakes and season with salt. Simmer for 10 minutes on a low heat, stirring every so often.
Add in the cooked spaghetti and a ¼ of the pasta water whilst stirring the sauce and pasta together.
Garnish with the chopped parsley and that's it!