Heat olive oil in a large pan and cook onion until it starts to soften. Add sausage, and break it into pieces with a wooden spoon as it cooks.
When sausage is no longer pink, add garlic and cook for 1 minute. Drain off any excess fat.
Add diced tomatoes, tomato sauce, tomato paste, basil, salt, red pepper flakes, and black pepper and simmer until thickened, about 15 minutes.
Meanwhile, cook pasta according to package directions. Drain and place drained pasta in a large bowl.
Add cream and simmer another 5 minutes, Turn heat to low and stir in Parmesan cheese.
Pour sauce over pasta and toss to coat.