01 - Preheat oven to 375°F. Toss bread cubes with olive oil, garlic powder, and salt. Spread evenly on a baking sheet and bake for 12 to 15 minutes, tossing halfway, until golden and crisp.
02 - Heat 2 tablespoons olive oil in a large pot over medium heat. Add diced onion, carrot, and celery, sautéing for 6 to 8 minutes until softened.
03 - Stir in minced garlic and cook for 1 minute until fragrant.
04 - Add tomatoes with their juices, fresh basil leaves, vegetable broth, sugar, salt, black pepper, and red pepper flakes if using. Stir and bring to a simmer.
05 - Reduce heat to maintain a gentle simmer, cook uncovered for 20 to 25 minutes, stirring occasionally, until vegetables are very tender.
06 - Remove from heat and puree the soup until smooth using an immersion blender or in batches with a regular blender.
07 - Stir in heavy cream and gently warm if necessary. Adjust seasoning to taste.
08 - Ladle into bowls and top with crispy croutons and additional fresh basil leaves for garnish.