01 -
Melt unsalted butter in a Dutch oven or large pot over medium heat. Add diced onion and cook, stirring occasionally, until softened, about 3 to 5 minutes. Add minced garlic, kosher salt, black pepper, and red pepper flakes if using. Cook until fragrant, approximately 30 seconds.
02 -
Incorporate crushed tomatoes and bring to a gentle simmer. Continue simmering, stirring occasionally, until the flavors are well developed, about 20 minutes. Prepare the pasta during this time.
03 -
Meanwhile, bring a large pot of generously salted water to a boil. Add rigatoni and cook 1 minute less than package instructions for al dente texture. Reserve 120 millilitres of pasta water before draining.
04 -
Return sauce to medium heat. Add heavy cream and reserved pasta water, stirring to combine and bringing the sauce to a gentle simmer. Fold in rigatoni, ensuring each piece is evenly coated.
05 -
Plate the rigatoni and finish with grated Parmesan cheese and chopped parsley if desired. Serve immediately.