In a small bowl, combine the ricotta cheese, parsley, basil and lemon zest. Refrigerate until ready to serve.
PREPARE THE SOUP:
Heat a large pot (Dutch oven, if you have one) over medium-high heat. Add the sausage and onion and cook, breaking up the meat with a spoon, for 5 to 6 minutes until no pink remains. Drain any fat.
Stir in the bell pepper and garlic and cook until slightly softened, about 3 minutes.
Add the whole tomatoes with the juice, breaking up the tomatoes with your hands as you add them. Stir in the broth, crushed tomatoes, Italian seasoning, salt and pepper. Bring to a boil, reduce the heat to a gentle simmer, cover, and cook for 10 minutes
Meanshile, bring a medium saucepan of salted water to a boil and cook the shells al dente according to the package directions, about 7 minutes.
Remove the soup from heat and stir in the spinach. Allow the soup for rest for 3 minutes.
Divide the shells among 6 bowls. Ladle the soup on top of the shells and top each portion with about 2 tablespoons of herbed ricotta cheese.