Fill a large pot with salted water and bring it to a rolling boil—this will take 8-10 minutes. While waiting, mince the garlic, chop the fresh parsley, and zest and juice the lemon. Measure out the olive oil, red pepper flakes, salt, and black pepper into small bowls for easy access during cooking. Having everything prepped and ready is essential for this quick, delicate sauce.

Once the water reaches a boil, add the spaghetti and cook according to package directions until al dente—usually 8-10 minutes. Just before draining, reserve 1/2 cup of the starchy pasta water in a small bowl or measuring cup, as this is crucial for creating a silky sauce. Drain the pasta and set aside.

Heat the olive oil in a large skillet over medium heat. Once shimmering, add the minced garlic and crushed red pepper flakes, stirring constantly for about 30 seconds—just until fragrant but before the garlic begins to brown. Add the chopped parsley and cook for another 30 seconds to soften it slightly. This gentle cooking blooms the flavors without burning them, which would create bitterness.

Add the lemon zest, lemon juice, salt, and the reserved pasta water to the skillet, stirring to combine. The pasta water's starch will help emulsify the oil and create a silky sauce rather than a greasy one. Immediately add the cooked pasta from Step 2 to the skillet and toss everything together for about 1 minute, allowing the noodles to absorb the bright lemon flavors. I like to keep a spoon handy to add a splash more pasta water if the sauce seems too dry—it should coat the noodles lightly, not be soupy.

Remove the skillet from heat and stir in the grated Parmesan cheese until it's evenly distributed and melts slightly into the warm pasta. Divide the pasta into serving bowls and top with extra parsley and additional Parmesan if desired. Serve immediately while hot, as this delicate lemon pasta is best enjoyed right away before the sauce cools and becomes heavy.