Basil and lemon are such bright, summery ingredients – this dish would also be delicious topped with grilled shrimp or chicken.
Bring a large pot of salted water to a boil over the medium-high heat and cook the spaghetti according to the package directions. Before draining, reserve about 1/2 cup of the pasta cooking water.
Drain the pasta, resturn it to the pot, and add the butter. Toss until the butter melts and coats the pasta.
Meanwhile, whisk together the olive oil, lemon juice, lemon zest and Parmesan cheese. Toss this with the buttered pasta and add some of the reserved pasta water to loosen it up a little.
Add the basil and toss gently. Season to taste with salt and pepper and serve right away.