Preheat oven to 180 degrees C. Grease an 20x20cm square cake tin.
Base: Rub together the butter, sugar and flour until crumbly. Sprinkle the mixture into the prepared tin and press down to form a base. Bake 20 to 25 minutes in the preheated oven until firm and slightly golden.
Topping: Place apricots and enough water to cover in a small saucepan over medium heat. Bring to the boil then simmer for 10 minutes. Drain and cool then chop coarsely.
In a large bowl mix together the eggs and brown sugar until well blended. In a separate bowl combine flour, baking powder and salt. Stir into the egg mixture. Mix in vanilla, walnuts and apricots. Spread mixture over baked layer.
Bake for 25 to 30 minutes in the preheated oven or until firm. Leave in tin and cool on cake racks. Cut into bars and sprinkle with icing sugar.