Begin by bringing a large pot of salted water to a rolling boil over high heat. Add the spaghetti and cook it according to package instructions until it reaches al dente, typically about 8–10 minutes. Reserve 1 cup of the pasta water before draining.

While the pasta cooks, heat a large skillet over medium heat and add diced pancetta or guanciale. Sauté for about 5–7 minutes until it becomes crisp and golden-brown.

In a mixing bowl, combine the eggs, finely grated Pecorino Romano cheese, and crushed red pepper flakes. Whisk until smooth and creamy.

Once the spaghetti has been drained, immediately add it to the skillet with the crispy pancetta. Toss thoroughly to coat.

Remove the skillet from heat and quickly pour the creamy egg mixture over the hot spaghetti, stirring vigorously.

If the sauce is thicker than desired, gradually incorporate reserved pasta water, stirring until smooth and creamy.

Dish out the pasta immediately, ensuring each serving is generously topped with coarsely grated Pecorino Romano and a sprinkle of freshly ground black pepper.