Melt butter in a large pot over medium heat, then add the chopped onion and cook until softened, about 5-7 minutes.

Stir in the minced garlic and cook for another minute until fragrant.

Pour in the canned whole peeled tomatoes, vegetable broth, and sugar, then bring the mixture to a simmer.

Reduce heat and let it simmer for at least 20 minutes to allow the flavors to meld.

Carefully transfer the soup to a blender or use an immersion blender to blend until smooth.

Return the blended soup to the pot, stir in the heavy cream and fresh basil, and cook for a few more minutes until heated through.

Season with salt and pepper to taste before serving.