Add spaghetti to a large pot of salted boiling water. Cook until it is just under done.
Meanwhile, juice and zest your lemon, grate parmesean cheese, and roughtly chop parsley.
Warm a second pot on the stove and once the pasta is ready. Using tongs place it in the warmed pan allowing some of the pasta water to drip in as well. Add the lemon and butter and stir for a minute or so until it becomes somewhat creamy, adding a little more pasta water if needed. Stir through parmesean until melted.
Plate and top with parsley, more parmesan, a spash of olive oil and salt and pepper.