Place the spaghetti in a pot of boiling salted water and stir immediately to prevent the strands from sticking. Cook the spaghetti to 'al dente'. Cut the garlic in half and rub the exposed area along the interior of a large serving bowl. The raw garlic flavor will coat the inside surface of the serving bowl. Discard the garlic. Add the freshly squeezed lemon juice and slowly drizzle in extra-virgin olive oil while whisking. Whisk until the ingredients have emulsified. Mix in the salt and Parmigiano cheese. When the spaghetti is 'al dente', drain and add to the serving bowl. Mix the pasta with the lemon sauce to coat evenly. Sprinkle the pasta dish with Parmigiano cheese, fresh parsley and lemon zest. Serve immediately.