Preheat the oven to 350°F / 180°C and line a large baking sheet with parchment paper. Place the tomatoes cut side up on the baking sheet, drizzle with 2 tablespoons of the olive oil, and sprinkle with salt and pepper. Roast until the edges just start to shrivel and the insides are still juicy – about 1 hour.
Heat the remaining 2 tablespoons of olive oil in a large pot over medium heat. Add the onions, carrots, garlic, and ½ teaspoon salt and cook until they become soft – about 8 minutes. Stir in the tomatoes, vegetable broth, vinegar, and thyme leaves and simmer for 20 minutes.
Let the soup cool slightly and blend until smooth consistency. Add the basil and pulse until combined.
Pour in bowls, garnish with basil leaves and serve with crusty bread.
