In a large pot or Dutch oven, heat the olive oil over medium heat. Add the chopped onion and cook until softened and translucent, about 5 minutes. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Pour in the crushed tomatoes and diced tomatoes (with their juices). Stir in the vegetable broth (or chicken broth), dried oregano, dried basil, and red pepper flakes (if using).
Bring the soup to a simmer, then reduce the heat to low, cover, and cook for at least 20 minutes, or up to 30 minutes, to allow the flavors to meld together.
Carefully transfer the soup to a blender (in batches if necessary) and blend until smooth and creamy. Alternatively, use an immersion blender to blend the soup directly in the pot.
Return the blended soup to the pot. Stir in the granulated sugar and heavy cream. Season with salt and freshly ground black pepper to taste. Heat gently until warmed through, but do not boil.
Ladle the creamy tomato soup into bowls. Garnish with fresh basil leaves and serve immediately. Optional: Top with grilled cheese croutons for an extra touch of indulgence.
Notes
Enjoy this creamy tomato soup with grilled cheese croutons for an extra touch of comfort!