Preheat oven to 350 degrees.
Beat egg whites until foamy. Gradually beat in 1/4 cup of sugar until stiff glossy peaks form. Set aside.

In a large bowl, cream butter, salt and vanilla. Gradually beat in 3/4 cups of sugar. Add egg yolks and beat until light and fluffy.

Remove 2 tbsp. of flour to a bowl and set aside. Sift remaining flour with baking powder. Mix into the butter/sugar mixture, alternating with milk, beginning and ending with dry ingredients.

Fold in egg whites.

Toss blueberries with the 2 tbsp. Of flour reserved. Fold lightly in to batter. Turn into greased 8 inch square pyrex or metal baking pan. Sprinkle remaining 1 tbsp. Sugar over.

Bake for 50 - 55 minutes until tester comes clean. Let cool. Sprinkle with powdered sugar and serve. Yummy!