Boil spaghetti in well-salted water until al dente. Reserve 1 cup pasta water.
Dice guanciale and cook in a dry pan over medium heat until crispy and golden.
Whisk eggs with finely grated pecorino and a lot of cracked black pepper.
Add hot pasta to the guanciale off the heat. Pour sauce, toss fast adding pasta water.
Plate immediately, finish with more pecorino and a crack of black pepper.