Heat olive oil in a large pot over medium heat. Add chopped onion and cook until translucent, about 5 minutes.

Add minced garlic and cook for another minute until fragrant.

Add canned diced tomatoes, vegetable broth, salt, and black pepper. Bring to a boil, then reduce heat and simmer for 15 minutes.

Use an immersion blender to puree the soup until smooth, or carefully transfer to a blender and puree in batches.

Stir in heavy cream and heat through. Serve hot with fresh basil or croutons if desired.