Preheat oven to 180°C (approximately 350°F).
For the dough, mix butter with sugar until creamy. Add egg, flour and salt and knead well.
Roll dough out on a baking sheet lined with baking paper.
Pre-bake dough for 15-20 minutes. Remove from oven and slightly cool.
For the topping, separate eggs. Beat egg whites with half the sugar until stiff. Mix yolks with half the sugar until foamy. Stir in lemon juice, lemon extract, vanilla pudding powder and flour. Fold in egg whites.
Pour topping over dough, smooth and bake for 35 minutes or until topping has set.
Allow to cool at room temperature.
Remove from baking sheet and cut into bars.
To serve, sprinkle with powdered sugar.