- Sift flour, baking powder, and salt together 3 times. 
- Beat egg whites until stiff and set aside. 
- Cream butter.  
- Mix sugar into butter. 
- Add egg yolks to the butter and sugar, beating well. 
- Add in dry ingredients, alternating with the milk. 
- Fold in egg whites, lemon juice, and the floured blueberries. 
- After scooping batter into a greased 10" cast iron pan, sprinkle top of batter with a 1/4 cup of mixed white and brown sugar. 
- Bake at 350 for 30 minutes.