Pour a good splash of olive oil into a large pot and bring up to a medium heat. Add onion, then garlic and chilli flakes.
Pour the tinned plum tomatoes into the pan. Stir well, and then bring up to the boil, and reduce to a gentle simmer for 10 minutes.
Get a potato masher and carefully help the tomatoes to break them down. Gently mash the tomatoes until crushed.
Season the sauce generously with salt, sugar (optional, but recommended) and stir in the chopped fresh basil.
Stir the cooked spaghetti through the arrabbiata sauce until well coated.