Preheat the oven to 425 degrees F. Also put a pot of water, covered, on the stove and bring to a boil.
Add a tbs or 2 of olive oil to a shallow ditch oven over medium heat. Add the onions and garlic along with a pinch of salt. Cook until softened, about 6-8 minutes, making sure not the burn the onions and garlic (lower heat if needed).
Add the tomato paste and stir to break up. Cook until it becomes a deep brick red, about 6 minutes. Once there, turn off the heat and add the vodka. Cook for a few minutes, or until you cannot smell strong alcohol. Return to heat.
Now slowly stir in the heavy cream until incorporated. Add the red pepper flakes and torn basil. Let simmer for about 15 minutes. (I like to add a pinch of salt and the pasta to the boiling water at this time.)
Once the pasta is 1 minute shy of al dente, reserve ½ cup of the pasta water and then drain and set aside.
Once the vodka sauce is a beautiful orange, add the ¼ cup of Parm and stir to combine. Remove from the heat and add the pasta directly to the sauce along with a bit of the pasta water if needed. Stir to combine.
Dot the ricotta all over the pasta, then top with the mozzarella and some more freshly grated parm.
Bake in the preheated oven for about 20-25 minutes, or until the cheese is melted and the sides are bubbling. Note: I like to change to the broil setting at the last 5-10 minutes to get a charred look. Make sure to keep an eye on the pasta if you do this.
Add some more parm and torn basil to the top before serving.