Salt the water well. Bring a large pot of water to a rolling boil and season generously with salt. It should taste like the sea so the pasta is well-flavored from the start.

Cook the spaghetti until just shy of al dente. Follow the package time, but start checking a minute early. You want the pasta to have a slight bite since it will finish in the pan.

Prep the garlic and parsley. While the water heats, thinly slice the garlic and chop the parsley. Keep them ready so nothing burns while you scramble.

Warm the olive oil gently. In a large skillet, add the olive oil over medium-low heat. You want a gentle sizzle, not a fry.

Toast the garlic to pale gold. Add the sliced garlic and cook slowly, stirring, until it turns light golden and fragrant. This usually takes 2–4 minutes. If it browns quickly, lower the heat. Burnt garlic is bitter.

Add red pepper flakes. Stir in the flakes for 15–20 seconds to bloom them in the oil. This releases flavor without scorching.

Reserve pasta water. Before draining, scoop out about 1 cup of starchy pasta water. This is your magic for emulsifying the sauce.

Combine pasta and sauce. Transfer the drained spaghetti straight into the skillet with the garlic oil. Toss to coat. Add a generous splash of reserved pasta water.

Emulsify and finish. Toss vigorously over low heat until the oil and water create a silky sauce that clings to the noodles. Add more water as needed. Season with salt and pepper to taste.

Stir in parsley and optional lemon. Off the heat, add chopped parsley and, if you like, a little lemon zest or a squeeze of juice for brightness.

Serve immediately. Plate hot. If using, top with a sprinkle of cheese or toasted breadcrumbs for texture. Enjoy right away.