Grab your favorite large pot or Dutch oven and heat the olive oil over medium heat. Once it’s shimmering (but not smoking!), toss in those sausage slices. Let them brown for about 2-3 minutes on each side until they develop caramelized edges.
Add the diced onion to the pot with the sausage. Cook until the onion starts to soften and becomes translucent – about 3-4 minutes. Then throw in the minced garlic and cook for another 30 seconds until it’s fragrant.
Pour in the chicken broth, scrape up any browned bits from the bottom of the pot.
Add the undrained diced tomatoes, Italian seasoning, and red pepper flakes. Stir to combine.
Add pasta to the pot. Make sure it's all submerged.
Bring the mixture to a boil, then reduce the heat to maintain a simmer. Cover the pot and let it cook for about 10-12 minutes, or until the pasta is tender. Give it a stir every few minutes to prevent sticking.
Once the pasta is cooked, stir in the heavy cream. Let it simmer for another minute or two until the sauce thickens slightly.
Remove the pot from the heat and sprinkle the shredded cheese on top. Cover the pot again and let it sit for a minute or two until the cheese melts.
Season with salt and pepper to taste.