Cook the pasta according to the package directions. Drain and cover with foil to keep warm.
Meanwhile, in a large saucepan or skillet, combine the marinara sauce and vodka. Set the pan over medium heat and bring to a simmer. Reduce the heat to medium-low and simmer for 5 to 10 minutes. Stir in the cream. Fold in the pasta.
Top with the mozzarella cheese, cover with foil or a lid and remove the pan from the heat. Let stand for 1 minute to melt the cheese.
Serve with parmesan cheese and red pepper flakes (if using).