1 cup freshly grated Parmigiano Reggiano, made into a paste (see instructions below)
1 teaspoon basil or parsley, minced
Fill a large pot with water and bring to a boil. While the water is coming to a boil, prepare the Parmigiano Reggiano paste. Place the grated cheese into a small bowl and add a few drops of water. Mush it around with your fingers until a thick paste is formed. Set aside.
Once the water is boiling, season it with a generous amount of salt. This is where you are adding the salt for the dish, so make sure it is salty enough to season the pasta. Add the spaghetti and cook until al dente.
While the pasta is cooking, melt the butter in a large sauté pan on low. Once it has melted, turn the heat off as you do not want the butter to brown. Add the lemon zest and lemon juice and stir to combine. Once the pasta has finished cooking remove it from the pasta water and add it directly into the pan with the lemon butter sauce. Add 1/4 cup pasta water. Vigorously swirl the pasta around in the pan, emulsifying the lemon sauce. Add the Parmigiano Reggiano paste, breaking it up into the pasta, continue stirring and coating the strands with the sauce. Add some freshly ground black pepper and your herb of choice. Stir to combine. Taste. If more salt is needed, add it now, stir and divide the pasta into individual bowls. Top with some freshly cracked pepper and a little sprinkle of basil or parsley.