Make the sauce. In a large deep sauté or frying pan, heat up the oil over medium heat. Add the cubed pancetta and cook, rendering the fat out of the pancetta, until it is crisp. Skip this step if you’re making vegetarian vodka sauce.
Add the onions and garlic and cook, stirring occasionally for 1-2 minutes. If you’re making spicy vodka sauce, here is where you add the red pepper flakes so they can bloom and release their flavor.
Add the vodka and bring the heat up to medium high and cook until the vodka is reduced by half.
Stir in the tomato paste, then the canned tomatoes, crushing them with the back of a wooden spoon. Bring to a simmer, cover and cook on low for 30 minutes to reduce and concentrate the flavors.
Mix in the cream and 1/4 cup of the reserved pasta water and let bubble, stirring occasionally. Taste and season with salt and pepper. Keep on very low heat while you cook the pasta.
Cook your pasta of choice 1-2 minutes shy of al dente in a large pot of salted water over high heat. Save 3/4 cup pasta water and drain well. The pasta will continue to cook in the sauce. Bring the sauce up to a simmer over medium high heat to reduce slightly. When reduced, add the drained pasta and cook, stirring, until the pasta is al dente and the sauce is very velvety and clings to the pasta, 1-2 minutes. Add extra pasta water by the tablespoon if the sauce gets too thick. Enjoy immediately with crushed red pepper flakes, freshly cracked black pepper, fresh basil, and parmesan cheese, if desired.