Step 1: Cook the Pasta

1. Bring a large pot of water to a rolling boil. Add salt and oil to the water to keep the pasta from sticking.
2. Add the penne pasta to the boiling water and cook according to the package instructions until al dente.
3. Once cooked, drain the pasta and set aside. Be sure to save a cup of pasta water for adjusting the sauce consistency later.

Step 2: Prepare the Creamy Tomato Sauce

1. Heat a dash of olive oil in a large skillet over medium heat. Add the chopped onion and sauté until it turns translucent and slightly golden.
2. Add the minced garlic and sauté for another minute until fragrant.
3. Stir in the tomato paste, salt, oregano, sugar, and chili flakes. Cook for 2-3 minutes to develop the flavors.
4. Pour in the water and milk, and let the sauce simmer for about 5 minutes. The mixture should start to thicken slightly.
5. Lower the heat and add the heavy cream, stirring continuously. Allow the sauce to come to a gentle simmer.
6. Add the shredded mozzarella cheese and butter, stirring until the cheese has melted and the sauce is creamy and smooth.
7. If the sauce is too thick, add a little reserved pasta water until you reach the desired consistency.

Step 3: Combine Pasta and Sauce

1. Add the drained pasta to the sauce, tossing well to ensure each piece of penne is beautifully coated.
2. Cook together for a few minutes on low heat to let the pasta absorb some of the sauce.
3. Serve hot, garnished with additional chili flakes and a sprinkle of oregano or fresh herbs if desired.