Dice the onion and finely mince the garlic cloves.
Heat the olive oil in a large skillet over medium to high heat. Once hot, add in the onion and garlic. Reduce the heat to medium, season with salt and pepper and cook until the onions are translucent, about 2-3 minutes. Be sure to stir occasionally to avoid any sticking or burning.
Add in the tomato paste and mix in with your spoon or spatula. Keep mixing until it is fragrant, about 1 minute.
Once fragrant, add in the tomato puree. Using the can, fill it half way with water, trying to get any left behind puree, and also add the water to the skillet. Mix it all together to combine. Raise the heat and bring the mixture to a boil. Once boiling, reduce the heat and simmer for 5 minutes or until slightly reduced and it begins to thicken.
Stir in the vodka and heavy cream. Simmer for another 5-7 minutes, this will cook out the alcohol in the sauce and thicken it. The sauce should easily coat the back of a spoon.
Taste your sauce and season it with salt, pepper and red pepper flakes.