How to Make It
Cook spaghetti according to package instructions in a pot of well-salted boiling water.
Meanwhile, in a large skillet set over medium heat, heat the butter until foaming, then add the red pepper flakes. Cook for about 30 seconds, then add the lemon zest. Cook for 30 seconds. When pasta is ready, add lemon juice to the sauce. Add the drained spaghetti and mix well. Serve.