03When water boils, add a couple of tablespoons of salt and pasta. Stir well and bring back to boil. Cook, stirring often. When pasta is cooked through but still firm, drain, reserving 1 cup cooking water.04Turn heat under skillet to low. Add about 3/4 of the sea urchin to skillet with a sprinkle of salt and a splash of pasta cooking water. Add pasta to skillet and toss thoroughly but gently over low heat, adding pasta cooking water and more oil to taste if mixture is dry. Taste for salt and toss in lemon zest, if using, and parsley. Serve hot, decorating each serving with remaining sea urchin.