Place ground sausage in a large skillet and cook over medium heat, stirring and crumbling as it cooks until sausage is browned but not cooked through.
Add in diced onion, garlic, black pepper and red pepper flakes and continue cooking until sausage is cooked through and onion is translucent.
Remove the sausage mixture from the skillet, leaving the drippings in the pan.
Add chicken broth the skillet and heat over medium-high heat stirring and scraping the cooked bits of sausage off the bottom of the pan with a wooden spoon to de-glaze the pan.
Add cream and bring to a low boil.
Turn down the heat and simmer the mixture for about 20 minutes. You want it to reduce to about ½ of the original volume.
While the sauce is simmering cook rigatoni to al dente in a large pot of water according to the package instructions, drain pasta and place back in the pot.
After the sauce has reduced, with the heat on low, add sun dried tomatoes, parmesan cheese, and spinach, cook, stirring frequently until cheese melts and spinach is wilted.
Pour sauce mixture over the cooked pasta and stir until the pasta is well coated with the sauce.
Serve Immediately.
Store any leftovers refrigerated in an airtight container.