Bring a large saucepan of water to a boil. Add spaghetti and cook according to package directions. Reserve 1/4 cup pasta water, then drain.
Return the pot to medium heat. Add butter, oil, thyme, lemon juice, lemon zest, salt, pepper and the reserved 1/4 cup pasta water. Stir to combine. Return the spaghetti to the pot along with Parmesan. Toss well to coat. Serve hot.