Halve and core pears, making sure you core enough to get a nice hollow inside the pear. Brush insides of pears with some of the lemon juice. Place in a greased baking dish, peel side down. If the pears won't sit in the baking dish properly, cut just a bit off the bottom to make the pears sit in the dish without wobbling.
In a bowl, combine the walnuts, currants, honey, brown sugar, lemon zest, cinnamon and remaining lemon juice. Spoon into pears. Dot with butter. Pour apple juice around pears. Bake, uncovered, at 180 C / Gas 6 for 30-40 minutes or until pears are tender, basting several times.