1) Make the filling: add the butter to a large saute pan and melt. Add the apples, sugar, cinnamon and lemon juice. Cook over medium heat until the apples are soft, about 15 minutes. Remove from the heat and cool.
2) When the filling is cool, roll the dough out on a lightly floured surface so that each piece forms a 17-20 cm circle. Place 2 to 3 tbsps of the filling on each pastry circle. Brush the edges of the circle with water. Fold the circle over the filling to make a half-moon shape. Seal by pressing the edges with the tines of a fork.
3) Preheat deep-fryer with oil to 180C.
4) Carefully add the pies to the oil, 1 at a time, and fry until golden brown, turning the pies as necessary for even browning, about 5 to 8 minutes. Drain on kitchen towels. Sprinkle with icing sugar immediately.