Cook rigatoni according to package directions. Reserve 1 cup pasta water before draining.
Melt butter in a large deep skillet over medium heat. Add onion and cook until soft, about 5 minutes. Add garlic and red pepper flakes and cook 1 minute more.
Pour in vodka and cook, stirring, until most of it evaporates, about 2 minutes.
Add crushed tomatoes, salt, and simmer for 10 minutes. Stir in heavy cream and simmer another 5 minutes.
Add drained pasta to sauce and toss to coat, adding pasta water as needed. Remove from heat and stir in Parmesan.
Serve topped with fresh basil.