Begin by bringing a large pot of salted water to a rolling boil over high heat. Once boiling, add the rigatoni and cook until al dente, which will be one minute less than the package instructions suggest. Reserve ½ cup of the pasta water, then drain the rigatoni and set aside.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the finely diced onion and sauté, stirring occasionally, for 5 to 6 minutes until the onion becomes soft and translucent. Then, add the minced garlic and cook for an additional 30 seconds, just until fragrant.

Stir in 2 tablespoons of tomato paste, followed by a 28-ounce can of crushed tomatoes, 1 teaspoon of Italian seasoning, and ½ teaspoon each of red pepper flakes, salt, and black pepper. Mix everything together well and let the sauce simmer on low heat for about 10 minutes.

Carefully transfer the hot marinara sauce into a blender. Add 1 ½ cups of cottage cheese and ¼ cup of grated Parmesan cheese to the blender. Blend the mixture until it becomes completely smooth and creamy.

Return the blended sauce to the skillet over low heat and add the drained rigatoni. Toss everything together gently until the pasta is fully coated with the creamy sauce. If you find the sauce too thick, gradually stir in some of the reserved pasta water.

Taste the Cottage Cheese Rigatoni and adjust the seasoning, adding more salt or pepper if needed. Once satisfied, serve immediately, garnished with chopped fresh parsley and additional grated Parmesan on top.