For a salad, it is better to take fresh and juicy vegetables.
Wash and peel the vegetables.
Grate the beetroot on a medium grater, chop the onion arbitrarily, not very finely.
Pour 1 tablespoon of olive oil (or vegetable oil) into a frying pan, add beets and onions, simmer over medium heat under the lid, stirring occasionally, for 5 minutes.
Add 2 tablespoons of vinegar, sugar and salt, reduce the heat and simmer for another 5 minutes, turn off the heat.
If the beet dries up and starts to burn, you can add 1 tbsp of water.