Cook the beetroot unpeeled until cooked, let it cool down, peel and grate. Peel the onion and fry in a little oil. Then add the beetroot and fry a little. Add the butter and season with the lemon, salt, sugar and pepper. The acidity of the lemon should come through well.
Tip:
You can also use vinegar as a substitute for the lemon, but then dose it more carefully. You can also use cooked beetroot.