Preheat the oven to 400°F (200°C).
Place the tomatoes, onion, and garlic on a baking sheet.
Drizzle them with olive oil and sprinkle with salt and pepper.
Roast for 30–35 minutes until the vegetables are soft and slightly browned.
Put the roasted vegetables into a blender or food processor.
Add the tomato paste (if using) and half of the broth.
Blend until smooth.
Pour the mixture into a pot.
Add the remaining broth.
Simmer on medium heat for 10–15 minutes.
Lower the heat and stir in the heavy cream.
Taste and adjust seasoning with more salt and pepper if needed.
Serve hot, topped with basil, cream, or croutons.