This light but filling soup will improve the digestion, support the liver and provide a hit of energy-boosting nitrates.
Place the beetroot in a large bowl with the olive oil, thyme and cumin seeds, season to taste and toss together.
Transfer to a baking sheet and place in a preheated oven, 200 (400), Gas Mark 6, for 30 minutes until the beetroot is tender.
Meanwhile, melt the butter in a large saucepan over a medium heat and add the onion.
Cook for 5 minutes, stirring frequently, until softened. Add the apple and cook for a further 5 minutes.
Add the beetroot and any juices to the pan along with the stock, bring to the boil and cook for 10 minutes.
Allow to cool slightly.
Place the soup in a blender or food processor, in batches if necessary, and blend until smooth.
Season to taste and reheat if desired.
Serve hot or cold, with a swirl of yogurt in the top of each bowl.