- Preheat oven to 450°F. Line large rimmed baking sheet with foil and spray foil with nonstick spray.
- Combine diced tomatoes, carrots, onion, salt, sugar, and pepper in large bowl and toss to combine. Transfer to prepared baking sheet and spread in single layer. Roast, stirring once, until vegetables are lightly browned, about 30 minutes.
- Heat oil in large saucepan over medium heat. Add garlic and red pepper flakes and cook, stirring constantly, until fragrant, 30 seconds. Add sherry and cook, stirring constantly, until almost evaporated, about 1 minute.
- Add roasted vegetables, crushed tomatoes, and broth and bring to boil. Reduce heat and simmer, uncovered, until vegetables are very tender, about 10 minutes. Remove from heat and stir in yogurt. Let stand to cool 5 minutes.
- Pour soup, in batches, into blender and puree. Return soup to saucepan and cook over low heat, stirring often, until hot, about 2 minutes. Remove from heat and stir in dill. Serve sprinkled with chives.
- Per serving (1 cup)
To store leftovers, transfer the soup to an airtight container and let cool. Cover and refrigerate up to 4 days or freeze up to 3 months.