1 To make the cake, mix together the flour, sugar, poppy seeds and a pinch of salt. Add the butter and the egg and quickly knead into a smooth dough. Wrap in cling film and chill in the fridge for 2 hours.
2 To make the filling, place the apples and the brown sugar in a pot and bring to the boil. Allow to bubble for a few minutes and then remove from the heat.
3 Heat the oven to 200°C (180°C in a fan oven), 400°F, gas 6 and line a baking tray with greaseproof paper.
4 Roll out the dough on a floured work surface to fit the baking tray. Place the dough on the prepared baking tray creating an edge all the way round. Top with the apple mixture and bake for around 30 minutes. Remove from the oven and leave to cool.
5 To make the meringue topping, turn on the grill function on the oven.
6 Beat the egg whites with the icing sugar until they can be cut with a knife. Spread onto the cake and place under the grill for 5-6 minutes until the meringue starts to turn brown. Before serving, leave to cool completely and cut into squares.