Bring a large pot of water to a rolling boil, then add 1 tbsp salt. Add spaghetti and cook until al dente according to package instructions. Reserve 1 cup of pasta cooking water before draining.

While the pasta cooks, place diced pancetta in a large cold skillet. Set over medium heat and cook, stirring occasionally, until the fat renders and the pancetta turns crispy and golden, about 5–7 minutes. Remove from heat.

In a medium bowl, whisk together eggs, Pecorino, Parmesan, and black pepper until well combined and creamy.

With the skillet off the heat, add the drained hot spaghetti directly into the pan with the pancetta and its rendered fat. Toss well. Temper the egg mixture by slowly whisking in a splash of hot reserved pasta water to warm it, then pour over the pasta. Toss vigorously, drizzling more pasta water as needed until a silky, creamy sauce forms. For food safety, ensure the sauce reaches 160°F (71°C). If it hasn’t, set the skillet over very low heat and stir constantly just until it reaches the temperature—do not scramble.

Divide among warm plates, top with extra grated cheese and a generous crack of black pepper. Serve at once while creamy.