Put the clams in a bowl with water and salt. Let them release the sand and soil. Change the water and repeat the process until they do not release more dirt. Fry the onion in the oil in a 16-inch pan until soft, stirring often. Add the tomatoes and the red pepper, salt to taste, stir well, and cook until tomatoes are reduced to a jammy sauce. Add the squid and cook, stirring, for a minute or so. Remove the pan from the heat and add the pimentón, stirring until you cannot see the powder and everything is mixed. Add the rice and stir well until the grains are coated. Place the pan on the heat and pour the shellfish stock over the rice; bring to a boil. Stir well and spread the rice out evenly in the pan (do not stir again). Lay the crab legs and the lobster tails on the top and cook over low heat for 20 minutes. Steam the clams with a finger of dry white wine in a pan with a tight-fitting lid. As soon as they open, they are cooked. Throw away any that have not opened. Add the clams and the liquid that they have released to the rice. After 10 minutes, add the shrimp and turn them when they have become pink on the first side. Add a little more hot stock toward the end if the rice seems too dry, but do not cook it any longer or the rice will be soggy. When the rice is done, turn off the heat and cover the pan with a clean cotton cloth. Let it rest for a few minutes. Enjoy. Serves 2.