Place the squash on a baking sheet and bake at 375°F for 30-45 minutes, or until the squash pierces easily with a butter knife and the interior is fully cooked.
Cut the squash in half and let it cool enough to handle. Scrape out the seeds and "goo" with a spoon; discard. Using a fork, scrape out the squash's "noodles" into a bowl; set aside.
Place the carrots, walnuts, garlic, oregano, lemon zest, red pepper flakes, and 1/4 teaspoon salt in a food processor. Pulse until finely chopped.
Heat oil in a large skillet over medium-high heat. Add the carrot-nut mixture and the raisins and cook, stirring frequently, until the carrots soften and begin to turn golden brown, about 5 minutes.
Add the vegetable broth and bring to a simmer.
Add the squash, cheese (if using), lemon juice, parsley, and toss. Adjust salt, to taste. Divide among bowls and top with more cheese (if desired).