Heat a non-reactive pot or enameled Dutch oven over medium heat. Melt butter and chopped onions.
Cook 10-12 minutes, stirring occasionally, until soft and golden. Add minced garlic and cook 1 minute, until fragrant.
Add crushed tomatoes with juice, chicken stock, chopped basil, sugar (or sugar to taste), and black pepper to taste.
Bring to a boil, reduce heat, partially cover with a lid, and simmer for 10 minutes.
For a blended/creamy soup, use an immersion blender to blend the soup in the pot to desired consistency or transfer to a blender in batches and blend until smooth (be careful not to overfill the blender with hot liquid), then return blended soup to the pot over medium heat.
Stir in 1/2 cup heavy cream and 1/3 cup freshly grated parmesan cheese. If needed, season with salt and pepper and turn off the heat.
Serve in warm bowls, topped with fresh basil and more parmesan.