Bring a large pot of generously salted water to a rolling boil. Add the spaghetti and cook until al dente according to package instructions, usually 8-10 minutes. Reserve 1 cup of pasta water before draining.

While the pasta cooks, heat the olive oil in a large, deep skillet over medium-low heat. Add the sliced garlic and cook slowly, stirring occasionally, until it becomes fragrant and turns a light golden color, about 2-3 minutes. Be careful not to burn the garlic or it will become bitter.

Add the red pepper flakes to the oil and garlic, cooking for another 30 seconds to infuse the oil with spice.

Once the pasta is cooked and drained, add it directly to the skillet with the garlic oil. Toss vigorously to coat each strand of pasta with the infused oil.

If the pasta seems dry, add a splash of the reserved pasta water to create a silky sauce that clings to the pasta.

Remove the skillet from heat and add the chopped parsley and grated Parmesan cheese. Toss again to combine everything thoroughly.

Season with salt and freshly ground black pepper to taste.

Serve immediately, garnished with additional Parmesan cheese if desired.