In a large pot of boiling salted water, cook the spaghetti according to package directions until al dente. This usually takes about 8-10 minutes. Reserve 1 cup of pasta water, then drain the pasta.
In a large skillet over medium heat, melt the unsalted butter.
Once the butter is melted and begins to froth, add the minced garlic. Sauté for about 1-2 minutes, or until fragrant and lightly golden, being careful not to burn it.
Stir in the red pepper flakes to add a bit of heat. Cook for an additional 30 seconds.
Add the drained pasta to the skillet, tossing to coat the spaghetti in the garlic butter sauce. If the pasta seems dry, gradually add reserved pasta water until you reach your desired consistency.
Season with salt and freshly cracked black pepper to taste. Toss again to ensure even distribution.
If desired, sprinkle in the grated Parmesan cheese, and toss until melted and mixed well throughout the pasta.
Remove from heat. Serve immediately, garnished with fresh chopped parsley.
Notes
Serve the pasta in deep bowls with an extra sprinkling of Parmesan and parsley on top. Drizzle some additional melted butter for a glossy finish!