Use a sharp knife or clean Stanley knife to score the skin of the pork at 1 cm (½ inch) intervals if it has not already been done. Sprinkle with salt and drizzle with 1 tablespoon of the oil then rub into the surface of the skin. Scatter the rosemary over the bottom of a roasting tin and sit the pork on top. Place on the lower rack of the halogen oven.
Set the temperature to 200°C (392°F) and cook for 45 minutes. While roasting, cook the potatoes in salted boiling water for 5 minutes until beginning to soften. Drain thoroughly and toss with the remaining oil.
Peel, core and thickly slice the apples. Scatter the apples and onion around the pork and pour over the cider. Arrange the potatoes on top and season to taste.
Return to the oven and cook for a further 30 minutes until the pork is cooked through and the potatoes are golden. Leave to rest for 20 minutes before serving with seasonal vegetables.