Roasted Green Tomato Basil Soup in Sourdough

Name: Roasted Green Tomato Basil Soup in Sourdough
Ingredients: 2 pounds ripe green tomatoes, sliced in half lengthwise; 1/4 cup extra-virgin olive oil; 1 tablespoon kosher salt; 1 1/2 teaspoons freshly ground black pepper; 1 tablespoon unsalted butter; 1 yellow onion, about 1 cup, coarsely chopped; 3 garlic cloves, minced; 1/4 teaspoon crushed red pepper flakes; 3 cups chicken or vegetable stock; 3/4 cup fresh basil leaves, packed; 1 teaspoon fresh thyme leaves; 2 to 4, whole round sourdough loaves; Sliced cherry tomatoes, for garnish (optional)