Season both sides with salt and pepper then place the breast skin down in a cold frying pan over low heat for a few minutes then gradually increase the heat to release the fat from the skin. Cook breast side down for around 6 minutes and once the breast has browned and crisp then flip over and cook for a few more minutes.
Pour away most of the fat from the frying pan (you can keep the fat and use for roasting potatoes later), add a knob of butter and the sugar and stir until the sugar has dissolved then stir in the cider vinegar. Cut the apples into 8 wedges and add to the caramel and cook for a few minutes on each side before pouring in the cider. Bring to a boil and cook for a few minutes until the sauce has reduced. If you prefer a rare to medium breast then remove the duck and keep warm while you make the sauce.
Leave the duck to rest before carving and serve with the sauce on warmed plates with braised spiced red cabbage and sauté potatoes.