Cook the spaghetti or linguine according to package instructions in a large pot of salted boiling water until al dente. Reserve 1 cup of pasta water, then drain the pasta.

In a large skillet, heat the olive oil over medium heat. Add the minced garlic and red pepper flakes, and sauté for about 2 minutes until the garlic is fragrant but not browned.

Add the cooked pasta to the skillet, along with the lemon zest and lemon juice. Toss to combine, adding reserved pasta water a little at a time until the desired consistency is reached.

Stir in the grated Parmesan cheese and season with salt and pepper to taste. Toss until the cheese is melted and the pasta is well coated.

Serve immediately, garnished with fresh parsley and additional Parmesan if desired.