1-Place a large saucepan of salted water over a high heat, bring to the boil. Add the pasta and cook according to packet instructions.2-While the pasta is cooking add the lemon zest to a separate pan along with the cream. Simmer for a 3-4 minutes until slightly reduced, stirring often. Add the butter, stir to combine. The butter should instantly melt into the liquid.3-Scoop the pasta into the sauce along with a little cooking liquid, toss to coat the pasta in the sauce, simmer for a minute or two until the pasta has absorbed most of the liquid. Remove from the heat and stir through two thirds of the cheese, little by little, keeping a little back to serve. Squeeze in the lemon juice, stir through and season to taste. Serve straight away in bowls with the remaining cheese and parsley sprinkled over the top.