In a large skillet, bring 6 cups of water and 3/4 teaspoon of salt to a boil. Add the dry spaghetti and cook for two minutes less than the package directions recommend.
Reserve a cup of pasta water before draining the spaghetti. Place the spaghetti in a bowl and keep it close to the stove to maintain warmth.
In the same pan used for cooking the spaghetti, melt 2 tablespoons of butter with the black pepper over medium heat. Cook until fragrant.
Add 1/2 cup of the reserved pasta water to the pan and stir until a glossy sauce forms.
Reduce the heat to low and add the spaghetti to the pan. Top with the grated Parmesan and the remaining 2 tablespoons of butter.
Use tongs to quickly mix the Parmesan, butter, spaghetti, and pepper sauce until a creamy sauce forms.
Serve immediately, garnishing with additional pepper and Parmesan cheese as desired.