Put 3tablespoons of the olive oil, garlic, and crushed red pepper in a 12-inch skillet and place over medium high heat. As soon as the garlic begins to sizzle, add the tomatoes and season with salt. Cook over medium high heat until all the liquid the tomatoes release has evaporated and the oil separates from the tomatoes, about 20 minutes.
Add the torn basil leaves and the optional pinch of crushed red pepper. Cook for 1-2 more minutes and remove from the heat.
While the sauce is cooking, Fill a pot for the pasta with about 6quarts of water, cover, and place over high heat. When the water boils and the sauce is ready, add 2tablespoons salt and the spaghettini and stir until all the strands are submerged. Cook until al dente. When the pasta is done, drain well, toss with the sauce and the remaining tablespoon olive oil, and serve at once.