Preheat your oven to 400°F (200°C).
Wash and halve the ripe tomatoes, placing them on a baking sheet, cut side up.
Drizzle the tomato halves with olive oil, and season with a pinch of salt and pepper.
Roast the tomatoes for 25-30 minutes until soft and slightly caramelized.
Sauté chopped onions and minced garlic in a soup pot until translucent and fragrant.
Add the roasted tomatoes to the pot.
Tear fresh basil leaves and add them to the pot, cooking briefly.
Blend the mixture until smooth using an immersion or countertop blender.
Return the mixture to the pot over low-medium heat.
Pour in heavy cream and stir to combine.
Season with salt and pepper, then simmer for 10-15 minutes.
Ladle the soup into bowls and garnish with fresh basil leaves if desired.