Bring a large pot of salted water to a boil and cook pasta until al dente.
While pasta cooks, fry guanciale or pancetta in a skillet over medium heat until crispy. Remove from heat.
In a bowl, whisk together eggs and Pecorino Romano cheese until well combined.
Drain pasta, reserving 1/2 cup of pasta water. Quickly toss the hot pasta with the egg and cheese mixture.
Add the crispy guanciale and a splash of pasta water to loosen the sauce if needed.
Top with freshly ground black pepper and serve immediately.