Follow these simple steps to create your delicious Creamy Pesto Zucchini Pasta:

1. Cook the Pasta: Bring a large pot of generously salted water to a rolling boil. Add the pasta and cook according to package directions until al dente (tender but still firm to the bite). Before draining, carefully reserve about 1 cup (240ml) of the starchy pasta water. Drain the pasta and set aside. Do not rinse the pasta, as the starch helps the sauce adhere.
2. Prepare the Zucchini: While the pasta is cooking, heat the olive oil in a large skillet or sauté pan over medium heat. Once shimmering, add the sliced or diced zucchini. Cook, stirring occasionally, for about 5-7 minutes, or until the zucchini is tender-crisp. You want it cooked through but not mushy – it should still have a slight bite.
3. Sauté Aromatics: Add the minced garlic (and optional red pepper flakes, if using) to the skillet with the zucchini. Sauté for about 1 minute more, until the garlic is fragrant. Be careful not to burn the garlic, as it can become bitter.
4. Create the Creamy Pesto Sauce: Reduce the heat to medium-low. Pour in the heavy cream (or half-and-half) and the basil pesto. Stir gently to combine everything thoroughly. Let the mixture heat through gently for 1-2 minutes, but do not bring it to a rapid boil, especially if using heavy cream, as it can sometimes separate or curdle if boiled vigorously after adding acidic ingredients like pesto.
5. Adjust Sauce Consistency: Stir in the 1/4 cup of vegetable broth or reserved pasta water. The starch in the pasta water will help emulsify and slightly thicken the sauce. If the sauce seems too thick for your liking, add more reserved pasta water or broth, one tablespoon at a time, until it reaches your desired consistency. Remember the sauce will thicken slightly more when the cheese is added and as it coats the pasta.
6. Incorporate Cheese: Remove the skillet from the heat (or keep it on the lowest possible setting). Stir in the 1/2 cup of grated Parmesan cheese until it melts smoothly into the sauce. Taste the sauce and season generously with salt and freshly ground black pepper to your preference.
7. Combine Pasta and Sauce: Add the drained pasta directly to the skillet with the creamy pesto sauce and zucchini. Toss gently but thoroughly using tongs or two large spoons, ensuring every piece of pasta is well-coated with the sauce and the zucchini is evenly distributed. If the pasta seems a bit dry, add another splash of the reserved pasta water to loosen it up.
8. Final Touches & Serving: Stir in the optional fresh lemon zest, if using, for a final burst of brightness. Serve the Creamy Pesto Zucchini Pasta immediately. Garnish generously with extra grated Parmesan cheese and perhaps a sprinkle of fresh basil leaves or parsley.