Melt the Butter: Begin by melting 2 tablespoons of unsalted butter in a Dutch oven or large pot over medium heat. As it melts, enjoy the fragrant aroma filling your kitchen. Make sure the butter is completely melted but not browned, which will take about 2 minutes.

Sauté the Onion: Add a diced yellow onion to the pot and sauté for 3 to 5 minutes, stirring frequently until the onion becomes translucent and soft.

Add the Garlic and Seasonings: Stir in 2 minced garlic cloves, along with kosher salt, black pepper, and optional red pepper flakes. Cook everything for about 30 seconds.

Incorporate the Tomatoes: Pour in a can of crushed tomatoes, mixing well with the sautéed ingredients. Increase the heat slightly to bring the sauce to a simmer. Permit it to bubble gently for about 20 minutes.

Cook the Rigatoni: While the sauce simmers, bring a large pot of salted water to a boil. Cook the dried rigatoni pasta according to the package instructions until it is al dente, about 10-12 minutes.

Combine Sauce and Cream: Return the tomato sauce to medium heat and stir in ½ cup of heavy cream along with the reserved pasta water. Bring this mixture to a gentle simmer for about 3-5 minutes.

Toss the Rigatoni with the Sauce: Once the sauce reaches the desired consistency, gently fold in the drained rigatoni pasta, ensuring every piece is well-coated.

Garnish and Serve: Transfer the creamy tomato rigatoni pasta to serving bowls and sprinkle with grated Parmesan cheese and chopped fresh parsley.