Preheat the oven to 400°F (200°C).

Cut the spaghetti squash in half lengthwise and scoop out the seeds.

Place the squash halves cut side down on a baking sheet lined with parchment paper or aluminum foil.

Bake for 30-35 minutes, or until the squash is tender and the strands easily separate with a fork.

Remove the squash from the oven and let it cool slightly. Use a fork to scrape out the squash strands and set aside.

In a large pot, heat the olive oil over medium heat. Add the chopped onion, carrots, and celery, and cook until the vegetables are softened, about 5 minutes.

Add the minced garlic, zucchini, and yellow squash to the pot and cook for another 2 minutes.

Pour in the vegetable broth and diced tomatoes, along with their juices. Add the Italian seasoning, salt, and pepper. Stir well.

Bring the soup to a boil, then reduce the heat and simmer for 15 minutes, or until the vegetables are tender.

Add the cooked spaghetti squash to the soup and stir well to combine. Simmer for another 5 minutes to heat through.

Serve the soup hot, garnished with grated Parmesan cheese and fresh basil.

Enjoy!