Clean and wipe dry the duck and to dry for at least 2-3 hours, placed on a wire rack.
Preheat the oven to 190°C.
Clean and wipe the oranges then cut one of them into slices. Peel the onions, then slice.
Season the cavity of the duck with salt and pepper, then stuff it loosely with onion and orange slices.
Rub the skin of the duck with salt and pepper, then scar it with crosses, using a sharp knife. Make sure not to cut into the meat!
Place the duck in a small baking tray and roast in the oven for about 60 minutes.
Meanwhile, juice the other orange and put it into a pan. Add the vinegar and bring it to the boil, then reduce by half into a thick, sticky sauce.
After 50 minutes of roasting, take the duck out of the oven, and test the legs if it’s cooked to your liking. If it is, pour the fat into a bowl and brush the duck with the balsamic-orange sauce. Put it back in the oven and roast for a further 10-15 minutes until golden brown.
Rest the duck on a plate covered with foil and tea towels, whilst you make a couple of side dishes and some gravy from the cooking juices.
Carve the duck and serve with the side dishes and the gravy.