Preheat your oven to 400°F (200°C).
Place the halved tomatoes, chopped onion, and garlic cloves on a baking sheet.
Drizzle with olive oil, and season with salt and pepper.
Roast in the oven for 30-35 minutes until the tomatoes are caramelized.
Remove from the oven and let cool slightly.
Transfer the roasted vegetables to a blender.
Add vegetable broth and sugar (if using).
Blend until smooth and creamy.
Pour the soup into a pot and heat over medium heat.
Adjust seasoning, and serve hot, garnished with basil and a drizzle of cream.