Preheat the oven to 180°C.
Cut the onion, beetroots and tomatoes in half, then put them in a large baking tray.
Cut the carrot into chunks and tuck between the vegetables together with the garlic cloves and chilli (if used). Scatter the thyme leaves on top, drizzle with the oil, then season with salt and pepper.
Bake for approx. 30 minutes, turning the veggies once or twice.
When the veggies are tender, transfer them to a saucepan. Remove the skin of the garlic cloves and the stem of the chilli.
Add the vegetable stock and chickpeas then bring to the boil. Add the coriander or basil leaves. Using a stock blender, process the stew into a silky soup.
Reheat it if necessary.
Add the cider vinegar just before serving.