Add sausage to a large skillet and sauté over medium heat, stirring, until all pink has disappeared, about 3-4 minutes. Add onions and red pepper flakes, and saute until onions are soft, about 3 minutes. Add the garlic and sauté an additional 30 seconds. Add vodka and simmer 2 minutes, shaking pan occasionally.
Increase heat to high and add cream. Boil until mixture thickens, about 2-3 minutes. Add tomato sauce, and cook 2 minutes or until sauce coats the back of a spoon. (NOTE: Sauce can be made 1 day ahead, and refrigerated until needed.)
Cook pasta in salted water until al dente. Bring sauce to simmer (if refrigerated). Toss pasta with sauce, ½ cup of Parmesan cheese, parsley and basil. Transfer to large bowl and sprinkle with remaining cheese. Serves 6.