For almond pastry, beat sugar, butter, orange and lemon rind, vanilla and orange-blossom water in an electric mixer until light and fluffy (4-5 minutes). Beat in eggs and yolk, add remaining ingredients and stir until a soft dough forms. Turn onto a well-floured surface, form one-third into a disc, then form remaining pastry into a disc. Wrap both pieces in plastic wrap and refrigerate to rest (overnight).
For Armagnac cream, bring milk, vanilla seeds, lemon rind and orange rind to the boil in a saucepan over medium-high heat. Meanwhile, whisk yolks, sugar and flour in a separate bowl to combine. Whisking continuously, pour milk mixture over yolk mixture, whisk to combine, then return to pan and whisk continuously over medium heat until thick and smooth (2-3 minutes). Remove from heat, whisk in Armagnac, rum and orange-blossom water, cover closely with plastic wrap and refrigerate until chilled (3-4 hours).
Preheat oven to 160C. Roll out larger almond pastry disc on a well-floured surface to 5mm thick and line base and sides of a 22cm-diameter, 3cm-deep fluted tart tin. Spread Armagnac cream over, filling to 1cm below rim (there may be a little mixture left over). Roll out smaller almond pastry disc on a well-floured piece of baking paper to 5mm thick, invert on top of Armagnac cream, peel off baking paper, press edges to seal then trim excess pastry. Lightly beat egg and cream in a small bowl and brush over pastry. Prick pastry top with a fork, cut three slashes in top for steam to escape and bake until dark golden (45-50 minutes). Cool to room temperature, dust with icing sugar, cut into thick wedges and serve with preserved sour cherries.
This recipe is from the July 2012 issue of Australian Gourmet Traveller.