Preheat oven to 350 degrees Fahrenheit.
Whisk together flour and cinnamon.
Mix in sugar and baking powder.
Add butter and stir until crumbly.
Add egg and work in. If the batter seems too dry/not crumbly enough, add an extra egg white.
Pour half of the batter into a 9" x 13" greased pan, then pour half of the blueberries on top. Repeat with remaining mixture and blueberries.
Bake for 35 minutes, cool, slice, and refrigerate. Serve cold.
20 servings
1 square