01 - Bring a large pot of salted water to a boil. Cook the pasta until al dente according to package instructions. Reserve 1/2 cup of pasta cooking water and drain the noodles.
02 - Heat olive oil in a large skillet over medium-low heat. Add sliced garlic and sauté gently for 2 to 3 minutes until fragrant and lightly golden, avoiding browning.
03 - Optionally, stir in crushed red pepper flakes and cook for 30 seconds.
04 - Add drained pasta to the skillet with garlic oil. Toss to coat evenly, adding reserved pasta water gradually until the sauce clings lightly to the noodles.
05 - Season with salt and freshly ground black pepper to taste. Remove from heat and stir in half of the parsley and half of the Parmesan cheese.
06 - Divide pasta among serving plates. Top with remaining parsley, Parmesan, and lemon zest if desired. Serve immediately.