Process flour, baking powder, butter and 75g caster sugar in a food processor until mixture resembles fine breadcrumbs. Add 2 egg yolks and process until mixture forms a ball; dough will be soft. Turn out onto a lightly floured work surface.
Reserve one-third of the dough; shape into a disc, cover with plastic wrap and refrigerate for 30 minutes. Using damp hands, press remaining dough into the base and sides of a greased and lined 20cm pie dish. Place pie shell in the refrigerator to chill.
Preheat oven to 180°C. To make filling, using an electric mixer, whisk egg whites to soft peaks, then gradually add remaining 75g sugar and whisk until thick and glossy. Fold in blackberries, vanilla and lemon zest until combined. Spoon into pastry shell and, using a small knife, slice off small pieces of reserved dough and place over filling to cover.
Bake for 50 minutes or until pastry is golden brown and a knife inserted into the centre comes out clean. Serve warm or cold dusted with icing sugar.
Reserve one-third of the dough; shape into a disc, cover with plastic wrap and refrigerate for 30 minutes. Using damp hands, press remaining dough into the base and sides of a greased and lined 20cm pie dish. Place pie shell in the refrigerator to chill.
Preheat oven to 180°C. To make filling, using an electric mixer, whisk egg whites to soft peaks, then gradually add remaining 75g sugar and whisk until thick and glossy. Fold in blackberries, vanilla and lemon zest until combined. Spoon into pastry shell and, using a small knife, slice off small pieces of reserved dough and place over filling to cover.
Bake for 50 minutes or until pastry is golden brown and a knife inserted into the centre comes out clean. Serve warm or cold dusted with icing sugar.