Heat the oil in a saucepan, add the onion and fry gently for 5 minutes until softened. Add the beetroot and apple, pour in the stock, season with salt and pepper and bring to the boil. Cover and simmer for 45 minutes, stirring occasionally until the beetroot is tender.
Allow the soup to cool slightly, then purée in batches in a blender or food processor until smooth. Pour into a large jug, taste and adjust the seasoning if needed, then chill in the refrigerator for 3–4 hours or overnight.
Pour the soup into bowls to serve and top with a spoonful of soured cream, sprinkle with the diced apple and pomegranate seeds, then drizzle with a little maple syrup. Serve extra maple syrup in a small jug to add as required and accompany with sliced rye bread, if liked.