Take the beetroot out of the package and collect the juice. Halve the beetroot, cut into slices and place in a bowl. Peel and quarter the onion, cut into fine slices and disassemble them. Mix the beetroot juice with water (approx. 200 ml juice + water) with brown sugar (2 tbsp), light rice vinegar (2 tbsp), tapioca starch (2 tsp), coarse sea salt from the mill (2 big pinches) and colored Pepper from the mill (2 big pinches stir until smooth. Heat the butter (2 tbsp) in a saucepan, add the onion strips and stir-fry vigorously. Deglaze with the prepared vinegar mixture and simmer for about 3 - 4 minutes, stirring constantly. The vinegar Pour the onion mixture over the beetroot and mix everything carefully.