Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente. Reserve about 1/2 cup of pasta water before draining.

While the pasta cooks, melt the butter in a large skillet over medium heat.

Add the minced garlic to the melted butter and cook for about 1 minute, or until fragrant. Be careful not to burn the garlic.

Stir in the lemon juice and Parmesan cheese. Cook for 1-2 minutes, or until the cheese is melted and the sauce is slightly thickened.

Add the drained pasta to the skillet with the lemon butter sauce. Toss to coat. If the sauce is too thick, add a little of the reserved pasta water, a tablespoon at a time, until you reach your desired consistency.

Season with salt, pepper, and red pepper flakes (if using).

Stir in the fresh parsley (if using).

Serve immediately.