In a large skillet, cook the pancetta over medium-high heat until the fat has rendered and it starts to brown, which should take about 4 minutes.
Add the chopped onions and crushed red pepper to the skillet, sautéing until the onions are soft and slightly caramelized, approximately 6 minutes.
Pour in the vodka and let it cook until it reduces, about 2 to 3 minutes.
Stir in the crushed tomatoes and mix well. Allow the mixture to cook for 15 minutes.
Next, add the heavy cream and continue cooking until the sauce thickens, which should take around 2 minutes.
Remove the skillet from the heat and stir in the grated Parmigiano-Reggiano.
Meanwhile, cook the penne ziti pasta in a large pot of salted boiling water until it is just al dente.
Drain the pasta in a colander, making sure to reserve 1 cup of the pasta water for the sauce.
Toss the hot pasta in the skillet with the vodka sauce to combine everything well.
Cook for an additional 2 minutes, adding reserved pasta water as needed to loosen the sauce.
Serve the pasta topped with extra grated Parmigiano-Reggiano.
