Let the oil infuse with the garlic and chili pepper for another 3-4 minutes on very low heat. To enhance the infusion tilt the pan on one side (see picture).
Pour in the crushed tomatoes or tomato pssata and bring the sauce to a simmer. Let it cook while the pasta cook, stirring occasionally. Season with salt and pepper to taste. If the sauce thickens too much, add a bit of the pasta water to reach your desired consistency.
When the pasta is done, remove the garlic and chili pepper from the sauce.
Add the pasta to the sauce and toss to coat the penne in the spicy tomato sauce. If the sauce is too thick, you can always add more pasta water to smoothen the sauce.
You can garnish your dish with some parsley if you like, but usually it's served plain and hot.