Prepare round cake tin. Preheat oven to 180 degrees C.
Cream butter or margarine and 1/2 cup brown raw sugar until fluffy.
Add salt and vanilla.
Separate eggs and reserve the whites. Add egg yolks to the sugar mixture; beat until creamy.
Combine flour and baking powder and add alternately with milk to mixture. Coat berries with flour and add to batter.
In a separate bowl, beat whites until soft peaks form. Add 1/4 cup of caster sugar, 1 tablespoon at a time and beat until stiff peaks form. Fold egg whites into batter. Pour into prepared cake tin.
Bake for 50 minutes or until cake tests it is done.