Preheat your oven to 400°F (200°C). Cut the spaghetti squash in half lengthwise and scoop out the seeds.
Drizzle the cut sides with 1 tablespoon olive oil and season with salt and pepper. Place cut-side down on a baking sheet.
Roast for 35-40 minutes, or until the squash is tender when pierced with a fork.
While the squash cooks, heat the remaining olive oil in a large skillet over medium heat. Add garlic and sauté for 1 minute.
Add zucchini, bell pepper, and broccoli to the skillet. Cook for 5-7 minutes until vegetables are tender-crisp.
In a food processor, blend the avocados, lemon juice, half the basil, and salt and pepper until smooth.
Once the squash is done, use a fork to scrape out the flesh into spaghetti-like strands.
Combine the squash strands with the sautéed vegetables and avocado sauce. Fold in the cherry tomatoes.
Garnish with remaining basil and optional Parmesan cheese before serving.