Heat olive oil and butter in a large skillet over medium heat
Add chopped onion and cook until soft
Add minced garlic and cook briefly
Stir in tomato paste and cook until darkened
Pour in vodka and simmer until reduced
Add heavy cream and stir until smooth
Season with salt, black pepper, and red pepper flakes
Simmer until the sauce thickens
Stir in grated Parmesan cheese
Add cooked pasta and toss to coat
Garnish with basil if desired