Bring a small pot of water to boil and cook pasta according to package directions. Drain and set aside. (See recipe notes)
Meanwhile: fill a large pot with water and bring to a boil. Chop rapini into 1 inch pieces, including the stalks.
Add chopped rapini to boiling water. Simmer for 1-2 minutes, then drain. Run under cold water to stop the cooking process. Set aside.
In the same pot, heat olive oil over medium heat. Brown sausage, breaking up as it cooks.
Stir in chopped onion and garlic. Heat, stirring occasionally, until onion is softened, about 5 minutes.
Add rinsed white beans, canned tomato, parmesan rind (if using) and chicken broth. Bring to a boil.
Stir in blanched rapini. Reduce heat and simmer on low for 20 minutes.
Taste and season with salt and pepper as desired.
To serve, place cooked pasta in bottom of each bowl, then top with soup and sprinking of grated parmesan cheese.
Serve with crusty bread, if desired.