Soften beet in salted water for 30-45 minutes. Immediately peel and cut into slices. Prepare dressing from vinegar, oil, salt, pepper and sugar, soak beets in it for 1 hour.
Remove the peel from the oranges with a sharp kitchen knife so that the white skin is also removed and fillet. Collect the juice and add to the lettuce. Remove the skin from the onion and cut into rings. 3.
Divide the frisée evenly on the plates, arrange the beet, oranges and onions on top. Grate a little horseradish on top.