Boil salted water and cook penne until al dente
Reserve some pasta water
Heat olive oil and butter in a large skillet
Add chopped onion and cook until soft
Add minced garlic and cook briefly
Stir in tomato paste and cook for 1 to 2 minutes
Add vodka and simmer until reduced slightly
Pour in heavy cream and stir until smooth
Add red pepper flakes, salt, and black pepper
Simmer the sauce until thickened
Add grated Parmesan and stir until melted
Toss in the cooked penne
Add reserved pasta water as needed to loosen the sauce
Mix until the pasta is fully coated
Serve with extra Parmesan and chopped basil or parsley