How to Make It
In a large, deep skillet, heat the olive oil. Add the garlic and cook over moderate heat, stirring, until softened and fragrant, about 2 minutes. Add the tomatoes, crushed red pepper and a generous pinch of salt and cook, stirring occasionally, until the tomatoes break down and form a sauce, 20 minutes. Season the sauce with salt; keep warm.
Meanwhile, in a large saucepan of salted boiling water, cook the tagliatelle until al dente. Reserve 1/2 cup of the cooking water, then drain well.
Add the pasta and half of the cooking water to the sauce and toss over moderately low heat until coated, 2 minutes; add more of the cooking water if the pasta seems dry. Transfer the pasta to shallow bowls and serve.