Directions

1. Bring a large pot of water to a boil. Generously salt water and return to a boil. Add spaghetti and cook, according to package directions, until al dente.
2. Drain spaghetti, reserving 1/2 cup pasta-cooking liquid, and return pot to stove. Add olive oil, garlic, and chile or red-pepper flakes; cook, stirring, over medium-low heat, 3 to 4 minutes. Add spaghetti and stir to coat. Add zest, lemon juice, basil, and reserved cooking liquid, if desired. Season with salt and pepper and stir to combine. Remove from heat.
3. Remove garlic and chile pepper, if using, and discard. Divide pasta evenly between 4 serving plates; serve immediately with cheese and drizzle with olive oil, if desired.