Cook ten minutes over low heat. Add tomato sauce and rice and coo k 5 minutes . Add boiling water, saffron and shrimp. Mix well and cook rapidly , covered, until liquid is absorbed, about 20 minutes. With a large spoon, tur n rice from top to bottom.
Steam mussels an d clams in a little water until their shells open.
Us the mussels, clams and pimientos as a garnish.