In a pan, heat the olive oil and to it add the onions (optional) and saute till slightly translucent. Then add the garlic and saute till the raw garlic smell disappears.
Stir in the red chili flakes and cook for a couple of seconds.
Add the chopped or crushed tomatoes. Stir everything well. Cover and cook for about 5 mins on medium heat.
When the tomatoes are slightly soft, add the salt and pepper and mix again. Cover and cook for another 10 mins stirring (medium-low heat) after every 2-3 mins to prevent the mixture from sticking.
Keep mashing the tomatoes with the spoon to crush them into a fine paste-like texture.
Stir in the tomato paste. This is optional but I prefer to add it as it gives the sauce a good color and slight texture/thickness. A little goes a long way. Cover and cook for another 5 mins (medium-low heat).
When the sauce is almost done add the parsley flakes, Italian seasoning, and sugar. Mix, mash and cover and cook for another 5 mins.
If at any time you feel the mixture sticking to the pan, add some water or pasta water ¼ cup at a time to the sauce. I added about ½ cup of pasta water at the end.
While the sauce is simmering, boil the pasta in a large pot as per package instructions. Drain it and reserve some pasta water.
To this drained pasta add the Arrabbiata sauce and Parmigiano Reggiano. Skip to keep it vegan. Mix well. If required adjust seasoning to taste and serve.
Easy and delicious Penne Pasta in Arrabbiata Sauce is ready. Serve penne Arrabiatta immediately topped with some freshly chopped basil and Parmigiano Reggiano with a side of Cheesy Garlic Bread or a salad of choice.