In a large skillet cook the onion, bell pepper and garlic in the butter
over moderate heat, stirring, until the vegetables are softened.
Stir in the pumpkin, broth, water, cream, nutmeg, salt and pepper to taste.
Simmer the sauce, stirring occasionally, for 10 minutes.
While the sauce is simmering, in a kettle of salted boiling water boil the
penne until it is al dente.
Ladle out and reserve about 1 cup of the cooking water, and drain the penne
Add the penne to the sauce. Cook the mixture over moderate heat, stirring
and thinning the sauce as desired with some of the reserved cooking water, for
1 to 2 minutes, or until the pasta is coated well.
Stir in the parsley.
Divide the pasta between 2 plates and serve it with the Parmesan cheese.