Preheat oven to 180 degrees C. In a medium bowl, mix together 1 1/2 cups flour, 1/4 cup sugar and 125g butter until the mixture is mealy. Press into the bottom of an ungreased 23x23cm pan.
Bake for 20 minutes in the preheated oven or until golden. In a medium bowl beat eggs until light and stir in the 3 tablespoons of lemon juice. Combine 1 cup sugar, 2 tablespoons flour, baking powder and salt (if desired); whisk into the eggs. Stir in the coconut. Pour over the baked crust and spread evenly.
Bake for 25 to 30 minutes in the preheated oven until centre is set and bars are golden. Cool and ice. To make the icing: in a small bowl, stir together the icing sugar and 2 tablespoons butter. Mix in the lemon juice 1 teaspoon at a time as needed for desired spreading consistency. Spread over cooled bars.