01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Arrange halved tomatoes, onion, garlic, and carrot on the baking sheet. Drizzle with olive oil and sprinkle with 1/2 tsp salt and black pepper. Roast for 25-30 minutes until tomatoes are soft and edges are caramelized.
03 - Melt butter in a large pot over medium heat. Add roasted vegetables, dried basil, thyme, and red pepper flakes. Stir for 2 minutes. Pour in vegetable broth, bring to a boil, then reduce heat and simmer for 10 minutes.
04 - Using an immersion blender, puree the soup until smooth. Alternatively, transfer to a countertop blender in batches and blend until creamy.
05 - Stir in heavy cream. Taste and adjust seasoning with remaining salt as needed. Serve hot, garnished with fresh basil leaves and a swirl of cream if desired.