Cook the pasta in salted water, draining it 1 or 2 minutes before it is al dente. It the meantime, heat the cream and zest in a saucepan, add butter one spoon after another, stirring constantly.
Mix the noodles with the cream mixture and pasta water, keep it on low heat and gradually add the cheese. Season with lemon juice, tarragon, salt and pepper.
Wait a little until the sauce thickens, serve with Parmesan cheese, freshly ground pepper and lemon zest.