Grate the onions and potatoes separately. Heat the oil, braise the onions and mince for about 10 min.
Wash and clean the peppers of their cores and seeds. With a knife, cut off their tops, to make a hole.
Salt the peppers on the inside and fill them with the stuffing. Arrange them in a tray, pour on the tomato juice, then evenly with oil.
Cover the tray with aluminum foil and put it in a preheated 392°F (200 °C) oven to bake about 30 min., then remove the foil and crisp briefly.