Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Peel, wash and slice the potatoes. Wash rosemary, pluck needles. Mix both with salt, pepper and 4 tablespoons of oil. Spread on a baking tray and bake in a hot oven for 40-45 minutes.
Onions peel, in rings cut or plane. Wash the thyme and remove the leaves. Dab steaks dry and fry in 2 tablespoons of oil for 2-3 minutes on each side. Season with salt and pepper. Let it rest wrapped in foil.
Heat 2 tablespoons of oil in the frying fat, fry the onions in it. Sprinkle with thyme and 1 tbsp. sugar, allow to caramelize. Deglaze with vinegar and 4 tablespoons of water, simmer for about 1 minute. Arrange everything.