Preheat oven to 300°F.

Bring a medium pot of salted water to a boil.

Add spaghetti and cook until al dente (about 8 minutes).

While water is heating, cook pancetta in an oven-safe skillet over medium heat until crisp.

Remove from heat and let cool slightly in the pan.

In a large bowl, whisk together eggs, pecorino, black pepper, and salt until smooth.

Add the cooled pancetta (and rendered fat) to the egg mixture and whisk to combine.

Drain the cooked spaghetti and add it to the skillet with the pancetta.

Add butter to the skillet and toss with the pasta until melted and coated.

Spread the pasta evenly in the skillet.

Pour the egg mixture over the pasta, distributing the pancetta evenly.

Sprinkle with additional black pepper.

Bake for 30-35 minutes, or until the frittata is set.

Rotate halfway through baking to ensure even cooking.

Check frequently toward the end to avoid overcooking.

Serve hot, warm, or at room temperature.