Preheat the oven to 200C (390F) and line a baking sheet with parchment paper.

Place tomatoes on the baking sheet, drizzle with olive oil, and season with salt and black pepper to taste. Bake for 25 minutes or until the tomatoes have brown spots on the skin.

Melt the butter in a stockpot over medium heat. Add onions, cook until softened, then add garlic, season with salt and cayenne pepper, and cook until golden. Remove from the heat.

When tomatoes are done, remove from the oven and place into the stockpot with onions and garlic. Season with salt and cayenne pepper and cook together for 2 minutes over a medium heat, stirring occasionally.

Add the chicken broth, bring to a light simmer, and cook for 5 minutes. Then, add the heavy cream, let the soup cook for an additional 2 minutes, taste, and add more salt if needed. Remove the pot from the heat and, using an immersion blender, cream everything together until smooth.

Pour into a soup bowl, garnish with some freshly chopped basil, and serve.