Bring a pot of generously salted water to a boil for the rigatoni (wait until step 6 to cook the pasta)

In a large pan over medium-low heat, sauté onions in 2 Tbsp butter with ¼ tsp kosher salt and ¼ tsp pepper for 15-20 mins (stirring often) until onions are tender, golden (not browned), and caramelized; remove from the pan and set aside (if you're short on time you can do this step in a separate pan while you make the red sauce)

Add 1 Tbsp butter to the pan and sauté the garlic over medium heat for 1 min; add the San Marzano tomatoes with their juice (squeeze them into small pieces with your hands as you put them in), Calabrian chili paste, sugar, ½ tsp more kosher salt, and vodka

Once the sauce starts bubbling, cover and simmer on low heat for 10 min, then uncover and simmer for 5 more mins (so the alcohol cooks off), breaking any tomato chunks into small pieces with your spatula

Add the cream and caramelized onions, and stir until combined, then turn off the heat until the pasta is ready

Boil pasta until very al dente (3 mins less than package directions), then transfer it into the sauce pan with a mesh strainer spoon to finish cooking, reserving the pasta water

Add ¼ cup pasta water to the pan and turn the heat to medium; toss the pasta in the sauce and cook for 3-4 minutes, stirring constantly, and adding pasta water as needed (I only added ¼ cup more) until the pasta is al dente (or desired tenderness)

Serve immediately with freshly grated parm and enjoy!