Wash the tomatoes very well. Cut them into halves. Place them on a baking sheet. Add sliced onions and garlic around them. Drizzle olive oil over everything. Sprinkle salt and black pepper evenly.

Place the baking sheet in a preheated oven at 400°F. Roast for about 35 minutes. The tomatoes should look soft and slightly browned. This roasting step gives rich flavor to the soup.

Place a large soup pot on medium heat. Add butter and let it melt slowly. Carefully transfer the roasted tomatoes, onions, and garlic into the pot. Stir gently for one minute.

Pour chicken broth into the pot. Stir everything together very well. Add sugar to balance the tomato acidity. Let the soup simmer gently for about 10 minutes to combine all flavors nicely.

Tear fresh basil leaves with your hands. Add them directly into the soup pot. The basil adds fresh and sweet flavor. Stir gently and cook for another two minutes before blending the soup.

Use an immersion blender carefully inside the pot. Blend until the soup becomes creamy and smooth. You can also use a regular blender. Blend in small batches for safety and easier handling.

Pour heavy cream slowly into the blended soup. Stir gently while cooking on low heat. The cream makes the soup rich and silky. Taste the soup and adjust seasoning if needed.

Ladle the warm soup into bowls. Top with Parmesan cheese and fresh basil. Serve with toasted bread or grilled cheese sandwiches. The soup tastes warm, creamy, and full of roasted tomato flavor.