01 - Heat olive oil in a large pot over medium heat. Add chopped onion and cook for 4 to 5 minutes until soft and translucent.
02 - Add minced garlic and cook for 1 minute until fragrant.
03 - Stir in tomatoes with their juice if canned, vegetable broth, sugar, salt, black pepper, and red pepper flakes if using. Bring mixture to a simmer.
04 - Reduce heat, cover, and simmer for 20 minutes, stirring occasionally.
05 - Add basil leaves and puree the soup with an immersion blender until smooth or blend carefully in batches using a countertop blender.
06 - Stir in heavy cream and heat gently for 2 to 3 minutes. Adjust seasoning as needed.
07 - Ladle soup into bowls and garnish with extra basil, a drizzle of cream, and freshly ground black pepper as desired. Serve hot.