Set a large, deep skillet over medium heat. Add the coarsely ground black pepper and toast it for about 1 minute, stirring often, until it smells fragrant.

Bring a large pot of lightly salted water to a boil. Add the spaghetti and cook it for 1 minute less than the package directions for al dente. Before draining, save about 1.5 cups of the starchy pasta water.

Use tongs to move the drained spaghetti straight into the skillet with the toasted pepper. Add the butter and 1 cup of the reserved pasta water. Toss continuously over medium-low heat for 1 to 2 minutes.

Take the skillet off the heat before adding the cheese. Add the grated Pecorino Romano a handful at a time, tossing hard with tongs after each addition. Add more reserved pasta water as needed.

Look at the sauce before serving. If it seems dry or clumpy, add a splash of hot pasta water and toss again until smooth.

Serve the Cacio e Pepe right away, twirling the pasta into nests on each plate, then finish with extra Pecorino Romano and a crack of black pepper.