Pulse flour, butter, and icing sugar in a food processor until breadcrumbs form, then add egg yolk and water.
Pulse until clumps form, then gather into a ball and knead briefly until smooth.
Grease a 23cm loose-bottomed, fluted tart tin.
Draw a circle on parchment paper 4cm wider than the tin base.
Roll the pastry out on the tin base until it reaches the marked circle.
Ease pastry into the tin and sides, prick with a fork, and chill for 30 minutes while preheating oven to 200°C.
Line with foil and beans, bake blind for 15 minutes, trim edges, and bake for 12 minutes more at 170°C.
Whisk filling ingredients, pour into the cooled case, and bake at 170°C for 35 minutes until just set.
Cool slightly, remove from the tin, and serve dusted with icing sugar.