To make pastry, put flours, sugar and butter in the bowl of a food processor. Process until mixture resembles breadcrumbs. Add egg yolk and water, then process until mixture begins to form a ball. Turn out onto a floured surface and knead until just smooth. Flour surface again and roll out pastry to a 30cm round. Lift 1 end of pastry over rolling pin and carefully lift into a 22cm-wide and 4cm-deep flan tin with removable base. Press pastry into tin. Trim edges. Refrigerate for 20 minutes.
Preheat oven to 180°C. Line pastry case with baking paper and fill with uncooked rice or baking beans. Bake for 10 minutes. Remove baking paper and rice or beans, then bake for another 10 minutes or until pastry is lightly golden on the edges. Remove pastry case from oven, set aside, and reduce temperature to 140°C.
To make custard, whisk eggs, sugar, cream and vanilla extract in a bowl until combined. Put pastry case on an oven tray. Pour custard into pastry case, then dot evenly with cherries. Bake for 45-50 minutes, covering pastry edges with foil if overbrowning, until just set in the middle (custard should still wobble when tart is gently shaken).
Stand tart, in tin, on a wire rack to cool. Refrigerate for 4 hours or overnight. Dust with icing sugar to serve.