Fill a medium sauce pan halfway with water.
Add the salt to the water and bring to a boil over medium high heat.
Add the spaghetti noodles and boil until al dente, about 6 minutes, stirring occasionally.
Meanwhile add the freshly ground pepper to a large skillet.
Add the butter.
Heat over medium low heat until butter is melted.
Add 1 1/2 cups of the pasta water to the skillet and bring to a simmer over medium heat.
Drain the pasta and add to skillet. Increase heat to medium high and cook until the liquid is absorbed, about 3 minutes.
Check the pasta for tenderness, continue cooking if too firm.
Add the grated cheese and stir until the cheese is melted and coats the noodles.
Plate and finish with extra freshly ground pepper and cheese if desired.