Peel the onion, cut it in half, then cut it into quarters. Now we cut each quarter into halves.
Put the sliced potatoes and onions in a baking dish (large enough for the vegetables to fit in one layer), pour in the olive oil and mix well.
Cover with foil and place in the oven at 200 degrees for 20 minutes.
Then increase the heat to 230 degrees, remove the foil, pepper, pour in the soy sauce and add sprigs of fresh thyme. Bake for another 30 minutes, stirring constantly. Potato slices with onions and soy sauce are ready.