Bring a large pot of salted water to a boil.
Cook the spaghetti according to package directions until al dente.
Reserve 1 cup of the starchy pasta water before draining.
While the pasta cooks, melt the butter in a large skillet over medium heat.
Once the butter foams, reduce the heat to low.
Add the lemon zest and minced garlic.
Cook for 1–2 minutes, stirring frequently, until fragrant.
Transfer the cooked pasta directly into the skillet.
Add ½ cup of the reserved pasta water and toss continuously until a light sauce forms.
Add half of the Parmesan cheese and toss until incorporated.
Stir in the lemon juice and remaining Parmesan cheese.
Continue tossing until the sauce becomes smooth and silky.
Add additional pasta water if needed to loosen the sauce.
Season with sea salt, black pepper, and additional lemon juice to taste.
Garnish the Lemon Pasta with extra lemon zest and fresh parsley or basil.
Serve immediately with additional Parmesan cheese.