1. Preheat oven to 400 degrees F.
2. Line a baking sheet with foil or parchment (to prevent sticking).
3. Add tomatoes and onion to the baking sheet. (I put my tomatoes cut side up so they maintain their juices).
4. Drizzle tomatoes and onion with olive oil, then sprinkle with salt and pepper.
5. Roast tomatoes and onion at 400 degrees for 45-50 minutes, or until starting to caramelize and very tender.
6. Let the veggies cool for a few minutes before transferring about half of the mixture to a blender.*
7. Add 1 clove garlic, 1 cup of the veggie broth, about half the basil to the veggies in the blender and puree until completely smooth. (Please work carefully and cover the top of your blender with a kitchen towel to prevent splatters).
8. Pour pureed soup into a large pot or Dutch oven and repeat the pureeing step with the second half of the veggies, basil, and broth.
9. Once all the soup is pureed and poured into the Dutch oven, warm the soup (if needed) over medium heat until heated through. Taste and add additional salt, pepper, or basil, as desired.
10. Garnish with a little fresh basil and enjoy!

*Alternatively, you can put all the roasted veggies, garlic, broth, and basil directly into the Dutch oven/soup pot and use an immersion blender to puree the soup.