Preheat the oven to 180°C. Grease a 23cm shallow square cake tin and line the base with baking paper.
Cream the butter and sugar until light and fluffy, then add the egg yolks and vanilla, beating well.
Sift together the flour, baking powder and salt and add to the creamed mixture alternately with the milk.
Scoop the mixture into the prepared tin and level the top.
To make the topping, beat the egg whites until soft peaks form and then fold in the sugar and coconut. Spread evenly over the cake.
Bake for 30 minutes or until an inserted skewer comes out clean. Leave in tin for 10 minutes before turning out carefully onto a wire rack to cool. To protect the topping reverse again immediately using another rack.
Variation Raspberry Macaroon Cake Spread 2 tablespoons raspberry jam over the cake before adding the macaroon topping.