Preheat oven to 350 degrees F (175 degrees C). Grease and flour an 8 inch square pan.
Cream butter or margarine and 1/2 cup sugar until fluffy. Add salt and vanilla. Separate eggs and reserve the whites. Add egg yolks to the sugar mixture; beat until creamy.
Combine 1 1/2 cups flour and baking powder; add alternately with milk to egg yolk mixture. Coat berries with 1 tablespoon flour and add to batter.
In a separate bowl, beat whites until soft peaks form. Add 1/4 cup of sugar, 1 tablespoon at a time, and beat until stiff peaks form. Fold egg whites into batter. Pour into prepared pan. Sprinkle top with remaining 1 tablespoon sugar.