Tonnarelli a Cacio e Pepe

Name: Cacio e Pepe
Ingredients: Kosher salt; 1½ pounds dried tonnarelli or spaghetti alla chitarra; ¼ cup olive oil; 2 tablespoons freshly ground black pepper; 2 tablespoons unsalted butter; 3 cups finely grated Pecorino Romano (about 6 ounces), plus more for serving; ½ cup finely grated Grana Padano (about 1 ounce)