For the beetroot salad, simmer the beetroot in boiling water for 1½ hours or until tender. Remove the beetroot from the water, allow to cool slightly, then peel. (I would recommend wearing rubber gloves when preparing the beetroots, to protect your hands from staining.)
Segment the beetroot into even pieces and mix with the remaining ingredients and one tablespoon of water. Season to taste with salt and freshly ground black pepper.
For the crème fraîche dressing, mix the ingredients together in a bowl.
To serve, arrange the beetroot salad in the centre the serving plates, top with the slices of sea trout and spoon the horseradish crème fraîche over or around. Garnish with a few sprigs of dill.