A large pot should be heated over medium heat with oil.
Add the onions and cook for 7–8 minutes, stirring occasionally, until softened.
Add the garlic and sausage and cook for another 7–8 minutes or until the sausage begins to brown.
Fill a separate large pot with water and bring it to a boil over high heat.
Add a generous pinch of salt to the water, then cook the pasta according to the package instructions.
Add the tomatoes to the pot with the sausage. If using whole tomatoes, blend them in a blender until smooth before adding.
Stir in the fresh basil, oregano, red pepper flakes, salt, and pepper. Bring the mixture to a boil, then reduce the heat and let it simmer.
Stir in the heavy cream and 1 cup of Parmesan cheese (reserve the remaining ½ cup for garnish).
The heat should be reduced to medium-low, and the sauce should simmer gently.
Drain the cooked pasta and add it to the sauce. Toss it to coat it evenly.
If you prefer a thicker sauce, let it simmer for 10 more minutes to reduce.
Taste and adjust the seasoning if needed.
Serve hot, topped with the remaining Parmesan cheese and fresh basil.