Preheat the oven to 165 degrees C. In a medium bowl, mix together butter, sugar, and 125 g flour. Press into the bottom of an ungreased 9x13 inch pan.
Bake for 25 minutes in preheated oven. In small saucepan, bring apricots and water to a boil, and cook for 10 minutes. Drain, chop, and set aside to cool.
In a medium bowl, beat eggs and brown sugar. Stir in 1/3 cup flour, baking powder, salt, vanilla, and lemon juice. Fold in nuts and chopped apricots. Stir in coconut, if desired. Pour over the prepared crust.
Bake for an additional 20 minutes in the preheated oven, or until firm. Cool, and dust with confectioners' sugar before cutting into squares.