01 - Heat olive oil in a large pot over medium heat. Add onion and carrot; sauté for 5 minutes until softened.
02 - Add garlic and cook for 1 minute until fragrant.
03 - Stir in diced tomatoes (with juices), basil, vegetable broth, sugar, salt, black pepper, and red pepper flakes if using.
04 - Bring to a simmer, reduce heat, and cook uncovered for 20 minutes, stirring occasionally.
05 - Remove from heat. Use an immersion blender to puree the soup until smooth (or carefully blend in batches in a blender).
06 - Stir in heavy cream. Reheat gently over low heat for 2–3 minutes. Adjust seasoning to taste.
07 - Ladle into bowls, garnish with fresh basil, and serve hot.