Bring a large pot two-thirds full of salted water to a boil over high heat. Add the pasta and cook until al dente according to the package instructions. Drain the pasta in a fine-mesh sieve, reserving 1 cup (8 fl oz/240 ml) of the pasta cooking water.
Return the pot to the stovetop and reduce the heat to medium. Add the butter. When the butter has melted, add the cooked pasta and toss t