1.Process almond meal, flours, 2 tablespoons of the sugar, xanthan gum, salt and butter until mixture resembles breadcrumbs. Gradually add ¼ cup (60ml) chilled water; process until mixture just comes together. Gently knead dough on a lightly gluten-free floured surface until smooth. Divide dough in half and shape each into a disk, enclose in plastic wrap; refrigerate for 30 minutes or until firm.
2.Meanwhile, make filling. Combine apple, sugar, ½ cup (125ml) water, juice and spices in a medium saucepan. Stir over low heat until sugar dissolves; bring to a simmer. Cook, covered, for 6 minutes or until apples are just tender and still hold their shape well. Using a slotted spoon, spoon apples into a bowl. Bring syrup in saucepan to simmer; cook for 3 minutes or until reduced. Pour syrup over apples in bowl; mix well and cool.
3.Preheat oven to 180°C/350°F. Lightly grease a 24cm round, 3cm deep pie tin.
4.Roll out each pastry portion between two sheets of baking paper into a 30cm round. Lift onto a tray; refrigerate for 10 minutes to firm. Line pie dish with pastry round. Cut remaining rolled pastry into 4cm wide strips. Spoon filling into pie case. Arrange pastry strips in a lattice pattern over filling. Trim pastry edge; reserving scraps if needed to re-roll pastry to complete lattice pattern. Brush lattice with egg; scatter with remaining sugar. Wipe rim clean. Transfer pie to an oven tray.
5.Bake pie for 45 minutes, on the lowest oven shelf, covering with foil if overbrowning. Leave pie in tin for 10 minutes before transferring to a wire rack to cool completely. Serve with gluten-free vanilla ice-cream, if you like.
Pie is best eaten on the day it is baked or freeze uncooked pie for up to
1 month. Cook from frozen, adding 5 minutes to the cooking time. Any leftovers can be reheated in the oven for 20 minutes.