Halve each tomato, cut out stem, peel garlic, peel onion and cut it in quarters.
Place tomatoes, garlic and onion in a greased 15"x10" x 1 "inch baking pan; drizzle with olive oil, sprinkle thyme on top, salt and pepper. Toss to coat.
Bake at 400°F for 25-30 minutes or until tender; stirring once. Cool slightly.
In a blender, process the tomato mixture and basil leaves in batches until blended. Transfer to a large saucepan and heat through. Garnish each bowl with salad croutons or extra basil leaves.