Peel and wash the potatoes. Peel the onion. Coarsely grate potatoes and onion. Stir in egg. Season with salt and pepper. Heat oil in portions in a pan. Fry 8 Rösti from the batter until golden brown, turning once.
Place the Rösti on a baking tray lined with baking paper. Wash, quarter and core the pears. Cut pear quarters into wafer-thin slices and sprinkle with lemon juice. Spread the pear wedges over the Rösti. Cut cheese into cubes and place on the pears. Bake the Rösti in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for 5-6 minutes. Arrange Rösti on plates and serve with cranberries