Once scraped and rinsed, cook the clams so as to allow them to open. Then remove the clams from the valve, drain them, keeping the water aside, put them at the side, keeping them warm.Blanch and shell the shrimps, then chop them coarsely. Clean the squids, removing the outside skin and the eyes; slice the tentacles and rinse the rest.Heat some oil in a saucepan with the chopped onion; once soften add the squids.After a few minutes cooking add the clams and then the shrimps. Mix, season with salt and pepper, add a handful of chopped parsley and cook stirring often.Next add the tomatoes, already blanched, peeled and deseeded and chopped into fillets.Simmer until ready, adding water if it starts drying up. Cook the pasta al dente and mix it to this sauce.