Sift together flour and sugar. Cut in butter until particles are the size of peas. Measure 3/4 cup of this mixture and reserve for the crumb topping.
Add baking powder, salt, egg yolks and milk to the remaining mixture. Beat for 3 minutes with electric mixer at low speed.
Beat egg whites until stiff but not dry. Fold gently but thoroughly into batter. Spread into well-greased and lightly floured 13 x 9 pan. Arranged blueberries on the top and sprinkle with reserved crumb mixture.
Bake in moderate oven (350 degrees) 40 to 50 minutes. Serve cold with whipped cream as a dessert, or warm as a coffee cake.
Preheat oven to 350 degrees. Grease a 13x9 baking pan.
Combine 2 cups flour, baking powder and salt in a bowl. With an electric mixer, mix butter and sugars until fluffy. Add eggs, one at a time, beating until just incorporated. Reduce speed to medium and beat in flour mixture alternately with milk in two batches until incorporated. Toss blueberries with remaining flour and gently fold into batter. Pour into prepared pan.
Scatter extra blueberries on the batter. Combine sugar with cinnamon and sprinkle over batter.
Bake cake until a toothpick inserted in the center comes out clean, 45 to 50 mins.