Boil the pasta. Bring a large pot of well-salted water to a rolling boil. Add the gluten-free pasta and cook according to package directions until just al dente. Before draining, reserve 1 cup of the starchy cooking water.

Warm the oil and garlic. While the pasta cooks, heat the olive oil in a large skillet over medium-low. Add the sliced garlic and red pepper flakes. Cook gently, stirring, until the garlic turns lightly golden and fragrant, about 2–3 minutes. Do not brown too much or it will taste bitter.

Add lemon and season. Turn off the heat. Stir in the lemon zest and 1 tablespoon lemon juice. Season the oil with a few pinches of salt and black pepper. Taste and adjust—there should be a bright, garlicky edge.

Combine with pasta. Add the drained pasta directly to the skillet. Pour in a generous splash of reserved pasta water and toss over low heat for 1–2 minutes, until the sauce loosens and coats the noodles. Add more water as needed to create a silky sheen.

Finish with herbs and cheese. Toss in the parsley and, if using, grated Parmesan. Stir until everything is glossy and lightly creamy. If it looks dry, add another spoonful of pasta water or a drizzle of oil.

Taste and serve. Finish with a bit more lemon juice, if you like, and extra pepper. Plate right away with an extra sprinkle of cheese and herbs on top.