If using bamboo skewers, soak them in water for about 30 minutes before cooking.
When ready to cook, preheat the barbecue to medium-high.
Using a knife, cut off any excess fat from the duck breasts and make shallow incisions in the skin in a grid-like pattern, taking care not to cut into the flesh. Cut each duck breast into eight cubes (not too small so the meat does not dry out).
Thread alternating cubes of duck meat, pineapple and red onion onto the skewers.
In a bowl, mix the soy sauce with the ponzu sauce and ginger.
Place the kebabs on the hot and oiled barbecue grill. Close the lid and grill the kebabs for 6 to 8 minutes, turning over several times and brushing with sauce regularly.
Soaking time (optional): 30 minutes
