Drain the beetroot, do not throw away the juice! Cut the beetroot into pieces, wash the apple, do not peel (!) And grate it roughly, peel the onion and dice it finely, put everything in a bowl.
Make a dressing from beetroot juice and the other ingredients and mix well with beetroot, apple and onion. Let it steep for at least 30 minutes.
Also tastes good the next day and is a really tasty alternative to cucumber salad and Co.