Cook the Pasta: Begin by boiling a large pot of salted water. Add the fettuccine or spaghetti and cook according to package instructions until al dente. Reserve 1 cup of pasta water and then drain the rest.
Prepare the Sauce: In a large skillet over medium heat, melt the butter. Add the minced garlic and sauté for 1-2 minutes until fragrant and golden, being careful not to burn it.
Add Cream: Slowly pour in the heavy cream and stir well to combine. Let it simmer for about 3-5 minutes until slightly thickened.
Incorporate Cheese: Gradually whisk in the grated Parmesan cheese until it melts and the sauce becomes smooth. If the sauce is too thick, add a little reserved pasta water to achieve your desired consistency.
Season: Stir in the red pepper flakes (if using), lemon zest, salt, and black pepper to taste.
Combine Pasta and Sauce: Add the drained pasta to the skillet and toss to coat the pasta evenly with the creamy sauce. Heat for an additional minute to ensure everything is well mixed.
Serve: Remove from heat, garnish with chopped fresh parsley, and an extra sprinkle of Parmesan if desired.
Notes
Add more or less red pepper flakes based on your spice preference.