Cook spaghetti in salted water until al dente according to package directions.
In a large skillet, heat olive oil and butter over medium heat.
Add minced garlic and red pepper flakes, sauté until fragrant, about 1-2 minutes.
Stir in lemon zest, lemon juice, and fresh parsley.
Add the cooked pasta to the skillet and toss with the sauce.
Season with salt and pepper to taste.
Add freshly grated Parmesan cheese and mix until creamy and well combined.