Moroccan Seafood Stew with Couscous

Name: Moroccan Seafood Stew with Couscous
Ingredients: 1 cup couscous; 2 tablespoons extra-virgin olive oil; 1 onion, halved and thinly sliced; 1 tablespoon paprika; 1 tablespoon ground cumin; Kosher salt and freshly ground pepper; 1 26-ounce box chopped tomatoes (such as Pomi) or two 14 1/2-ounce cans diced tomatoes; 8 ounces green beans, trimmed and cut into 1-inch pieces; 1/2 cup pitted green olives, plus 1/4 cup brine; 1/2 cup roughly chopped fresh cilantro, plus more for topping; 2 pounds mussels, scrubbed and debearded; 12 ounces medium shrimp, peeled and deveined