Cook the pasta in 3-4 l boiling salted water (1 teaspoon salt per litre) according to the package instructions.
Wash parsley and shake dry, pluck the leaves and chop them coarsely. Peel onion and garlic and chop very finely. Cut some olives into thin rings and put aside. Purée the rest of the olives with parsley and 2 tbsp. capers with a hand blender to a paste.
Stir in onion, garlic, olive rings, remaining capers and oil. Season salsa with salt and pepper.
Drain the noodles and collect some cooking water. Put the noodles back into the pot, mix immediately with the salsa. If necessary, stir in some cooking water. Season again with salt and pepper.