Heat grill to high. Grate the zest from half the lemon and squeeze the juice from both halves. Split the pork fillet pieces down the centre, cutting almost all the way through, and open out like a book. Lift onto a baking tray and season with salt, pepper and the lemon zest. Sprinkle with 1 tbsp of the sage. Grill for 8-10 mins, turning once, until cooked through
Meanwhile, pour the lemon juice into a small pan. Add the apple to the pan with the remaining sage, sugar, salt and pepper. Bring to the boil, stirring, and then simmer until soft, about 6 mins. Serve with your favourite green veg and potato wedges
