It pays to use high-quality extra-virgin olive oil in this dish.
1 pound spaghetti
6 tablespoons extra-virgin olive oil
12 garlic cloves, minced
3/4 teaspoon red pepper flakes
3 tablespoons chopped fresh parsley
2 teaspoons lemon juice
1 ounce Parmesan cheese, grated (1/2 cup)
Bring 4 quarts water to boil in large pot. Add pasta and 1 tablespoon salt and cook, stirring often, until al dente. Reserve 1/3 cup cooking water, then drain pasta.
Meanwhile, heat 3 tablespoons oil, two-thirds of garlic, and 1/2 teaspoon salt in 10‑inch nonstick skillet over low heat. Cook, stirring constantly, until garlic foams and is sticky and straw-colored, about 10 minutes. Off heat, add remaining garlic, pepper flakes, parsley, lemon juice, and 2 tablespoons reserved cooking water.
Transfer drained pasta to warm serving bowl. Add garlic mixture, remaining 3 tablespoons oil, and remaining reserved cooking water to pasta and toss to combine. Season with salt to taste and serve immediately, passing Parmesan separately.