01 - Heat olive oil in a large pot over medium heat. Add onion and cook for 4–5 minutes until softened and translucent.
02 - Stir in garlic and cook for 1 minute until fragrant.
03 - Add tomatoes with juices, vegetable broth, sugar, salt, pepper, and red pepper flakes. Bring to a boil, then reduce heat and simmer uncovered for 20 minutes, stirring occasionally.
04 - Add fresh basil leaves, then use an immersion blender to puree the soup until smooth. Alternatively, carefully transfer the soup in batches to a countertop blender and blend until smooth, then return to the pot.
05 - Stir in the heavy cream and heat gently over low heat for 2–3 minutes. Adjust seasoning to taste.
06 - Serve hot, garnished with extra basil leaves and a drizzle of cream if desired.