The name of this classic Italian sauce translates to "angry"—that is, spicy—but feel free to adjust the level of heat to your own taste. Slideshow: More Spaghetti Recipes
Heat the olive oil in a large saucepan over moderate heat. Add the garlic and red pepper flakes and cook, stirring, until golden and fragrant, 1 to 2 minutes. Add the tomatoes and cook, stirring occasionally and crushing them with a wooden spoon, until slightly thickened, about 30 minutes. Season to taste with salt and pepper.
Meanwhile, cook the spaghetti in a large pot of boiling well-salted water until al dente. Serve immediately, topped with the arrabbiata sauce.
The arrabbiata sauce can be made up to 3 days ahead and refrigerated in an airtight container. It can be frozen for up to 1 month.