Bring a large pot of salted water to a rolling boil. Add 8 oz of gemelli pasta and cook according to package instructions until al dente, usually about 8–10 minutes. Reserve ½ cup of pasta water before draining the pasta. Set the pasta aside.
While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat. Add 3 cloves of minced garlic and sauté for about 1–2 minutes until fragrant and lightly golden. Be careful not to burn the garlic, as it will turn bitter.
Pour 1 cup of heavy cream into the skillet with the garlic. Stir to combine and bring to a gentle simmer. Let the cream reduce slightly, about 3–4 minutes, stirring occasionally.
Add the zest and juice of 1 lemon to the cream sauce. Stir well to combine. Then, slowly add 1 cup of grated Parmesan cheese, stirring continuously until the cheese melts completely and the sauce becomes smooth. If the sauce seems too thick, add a splash of the reserved pasta water to loosen it to your desired consistency.
Add the drained gemelli pasta directly into the skillet with the sauce. Toss gently but thoroughly to coat every twist of pasta in the creamy garlic lemon sauce. Season with salt and freshly ground black pepper to taste.
Remove from heat and sprinkle freshly chopped parsley over the top for a burst of color and fresh herbal notes. Serve immediately with extra Parmesan on the side if desired.
