Wash the beetroot, dry it and wrap it in aluminum foil with the shiny side inside. Cook in a non-preheated oven at 180 ° C for about 90 minutes. Let the vegetables cool down a bit, then peel and slice them into thin slices.
For the marinade, mix the ingredients together with the exception of the oil and season to taste. Let the beetroot slices soak for about 30 minutes, turning more often. Finally mix in the rapeseed oil. Arrange the salad on small plates and sprinkle with chives.