The dried stigma from Crocus sativus, saffron adds flavor and golden color to a variety of Middle Eastern, African and European foods. Soak it in a little water, wine or broth for about 30 minutes before adding to a dish to help release its delicious flavor. Find it in the spice section of supermarkets, gourmet shops. It will keep in an airtight container for several years.
To clean mussels, rinse very well under cold running water and use a stiff brush to remove any barnacles or grit from the shell. Discard any mussels with broken shells or any whose shells remain open after you tap them lightly. Pull off any fibrous “beard” that might be pinched between the shells; the “beards” of most cultivated mussels are already removed.
Bring a large pot of water to a boil. Cook pasta according to package directions. Drain and transfer to a large serving bowl. Cover to keep warm.
Meanwhile, heat oil in a large saucepan over medium heat. Add garlic and cook, stirring, until it just begins to color, 2 to 3 minutes. Carefully add crushed tomatoes and saffron with soaking liquid (the mixture may splatter) and bring to a simmer. Cook, stirring frequently, until thickened slightly, about 5 minutes.
Meanwhile, bring mussels and wine to a boil in a Dutch oven (or other large pot) over high heat. Cover, reduce heat to medium and cook until the mussels open, 4 to 6 minutes. Transfer the mussels with a slotted spoon to a large bowl. (Discard any unopened mussels.)
Strain the mussel broth through a fine-mesh sieve into the tomato sauce. Stir in crushed red pepper and simmer over medium heat for 1 minute. Season with salt and pepper. Ladle about half the sauce over the pasta and toss to coat. Divide the pasta among 4 pasta bowls, top with mussels and spoon the remaining sauce over the mussels. Serve topped with parsley and lemon zest.