Heat olive oil in large pot over medium heat. Add onion, garlic, red pepper flakes and bay leaf. Cook for 5 minutes stirring often. Stir in diced tomatoes and cook for 8 minutes stirring and mashing some of the tomatoes with the back of a spoon. Add brown sugar and the broth and bring to a boil. When soup comes to a boil reduce the temperature and simmer for 10 minutes. Remove the bay leaf. Puree the soup in small batches in a blender or use an immersion blender. Only put small amounts of the hot soup in the blender so as not to have hot soup exploding from the top of the blender. When you are done pureeing return soup to the pot and add the heavy cream. Heat through. Stir in the basil and season with salt and pepper. Ladle soup into bowls and top with a cheese toast.