Boil a large pot of salted water and cook rigatoni until al dente. Reserve 0.5 cup of pasta water before draining.

Heat olive oil in a large skillet over medium heat. Add diced red onion and cook until translucent, about 5 minutes.

Stir in minced garlic and cook for 1 minute until fragrant.

Add tomato paste to the skillet, cooking for 3 to 4 minutes until it darkens in color.

Pour in the heavy cream and red chili flakes. Stir continuously until the sauce becomes smooth and homogeneous.

Add the cooked rigatoni to the skillet. Toss thoroughly, adding reserved pasta water a little at a time until the sauce reaches desired thickness.

Garnish with grated Parmesan cheese and fresh chopped parsley before serving.