Allow the squash to cool slightly, then use a fork to scrape out the squash into “spaghetti” strands. Place the noodles in a colander or strainer and rest for 10 minutes to remove any extra moisture.
In a bowl, combine the pesto, Parmesan, and squash noodles. Toss until well combined. Taste, and add additional salt or pesto as necessary. (Leftovers store in the refrigerator for a few days; you may have to refresh the flavor with additional pesto.)