In a large skillet over medium heat, melt better with oil; add onion and saute for 8 minutes or until transparent.
Add tomatoes and cook for 25 minutes or until almost no liquid remains in skillet; stir frequently.
Increase heat and add cream, vodka and red pepper flakes; boil for 2 minutes or until thickened to sauce consistency. Season to taste with salt and pepper.
Bring a large pot of lightly salted water to a boil. Add penne and cook for 8 to 10 minutes or until al dente; drain and transfer to a large bowl.
Bring sauce to a simmer and pour over pasta; toss to coat. Sprinkle with Parmesan cheese; serve.
