Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9x13-inch baking dish.

In a large bowl, stir together flour and sugar. Cut in butter using a pastry blender or a fork until pea-sized. Measure out 3/4 cup of the mixture, and set aside. Stir baking powder and salt into remaining mixture; mix in egg yolks and milk using an electric mixer on low speed for 3 minutes.

In a large glass or metal bowl, whip egg whites just until stiff peaks begin to form. Fold egg whites into batter. Spread batter evenly into the prepared pan. Sprinkle blueberries over batter and sprinkle reserved crumb mixture on top.

Bake for 40 to 50 minutes in the preheated oven, or until cake springs back when lightly touched in the center.