Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easy cleanup.

Place the halved tomatoes and chopped red peppers on the baking sheet. Drizzle with olive oil and sprinkle with salt and pepper.

Roast the vegetables in the oven for 25-30 minutes until they are slightly charred and softened.

In a large pot, heat a tablespoon of olive oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.

Add the minced garlic and cook for an additional minute until fragrant.

Remove the roasted tomatoes and peppers from the oven and add them to the pot.

Pour in the vegetable broth and balsamic vinegar. Bring the mixture to a simmer and let it cook for about 10 minutes.

Using an immersion blender, puree the soup until smooth and creamy. Alternatively, let it cool slightly and blend in batches in a stand blender.

Taste and adjust seasoning, adding more salt and pepper as necessary.

Serve hot, garnished with fresh basil leaves if desired.