Boil pasta in salted water until just shy of al dente.
Cook guanciale in a skillet over medium heat until crisp and golden; remove from heat but keep the rendered fat.
Whisk eggs and cheese together in a bowl until creamy; season generously with black pepper.
Drain pasta, reserving about ½ cup of cooking water.
Combine pasta with guanciale fat and toss off the heat.
Add egg mixture, stirring quickly so it coats the pasta without scrambling.
Adjust texture with a splash of reserved pasta water until glossy and silky.
Serve immediately, topped with guanciale and extra Pecorino and pepper.