Serving this pasta will remind you of dining in your favorite restaurant.
Melt butter in a pot. Sauté onion and garlic until translucent (about seven minutes).
Add in drained spinach and sauté two minutes more. Add in heavy cream and sour cream and stir until melted.
Stir in Parmesan cheese, salt, and pepper. Simmer for five minutes.
Prepare penne according to package instructions. Mix with pasta sauce.
This sauce keeps well in the refrigerator for five days.