Cook the pasta:
Bring a large pot of salted water to a boil. Add the spaghetti and cook until al dente according to package directions. Reserve ½ cup of pasta water, then drain.
Make the sauce:
In a large skillet, melt the butter with olive oil over medium heat. Add the minced garlic and cook for 1 minute until fragrant.
Add the lemon:
Stir in lemon juice and zest. Allow the mixture to simmer for 1–2 minutes to release the citrus flavor.
Create the creamy base:
Pour in the heavy cream and whisk until the sauce becomes smooth.
Add cheese:
Stir in grated Parmesan until it melts into the sauce. Adjust with a splash of pasta water if the sauce is too thick.
Combine:
Add the cooked pasta to the sauce and toss well until each strand is evenly coated. Season with salt and black pepper to taste.
Serve:
Garnish with chopped parsley, extra Parmesan, or more lemon zest. Serve immediately while warm.