Trim the stems and cores from the tomatoes, then roughly chop. Remove the seeds and ribs from the bell pepper and slice. Peel and quarter the onion. Smash and peel the garlic cloves. Add everything to a baking sheet and drizzle with the olive oil. Season with salt and pepper.
3. Step
Roast for 30 minutes, until the vegetables are browned on the edges and fragrant.
4. Step
Transfer the roasted vegetables to a slow cooker. Add the oregano, thyme, tomato paste, and vegetable stock.
5. Step
Cover and cook on high for 2 hours.
6. Step
Using an immersion blender or a standing blender, puree the soup until creamy.
7. Step
Stack and roll the basil leaves, then thinly slice. Add some to the soup and stir to incorporate.
8. Step
Ladle the warm soup into bowls and garnish with more basil.
