Preheat oven to 425F and spread tomatoes, onion, and garlic on a sheet pan.

Drizzle with olive oil, salt, and pepper, then roast 30 to 35 minutes until caramelized.

Transfer the roasted vegetables to a pot and add broth.

Simmer 5 minutes, then add basil.

Blend until smooth with an immersion blender.

Adjust seasoning and serve hot.