8 Roma tomatoes, halved and seeded
2 red peppers, quartered and seeded
1 medium onion, quartered
8 cloves garlic
2 teaspoons chopped fresh thyme leaves
4 tablespoons olive oil, divided
2 tablespoons balsamic vinegar
Kosher salt and freshly ground black pepper
1 (6-ounce) can tomato paste
6 cups vegetable stock
1/4 cup loosely packed chiffonade basil leaves
Special Equipment: Blender or immersion blender