Heat the olive oil in a large pot over medium heat.

Add the chopped onion and sauté until translucent, about 5 minutes.

Add the minced garlic and cook for another 1-2 minutes.

Stir in the diced tomatoes and vegetable broth. Bring to a boil.

Reduce heat and let it simmer for about 20 minutes.

If using, add the sugar to balance the acidity of the tomatoes.

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

Season with salt and freshly ground black pepper to taste. Stir in the fresh basil.

If desired, add the heavy cream and mix well.

Serve hot with a garnish of fresh basil, if desired.