Preheat oven to 350°F.
Grease an 8x8 dish with cooking spray.
In a large bowl, cream sugar, butter, & egg with a mixer until light and fluffy.
In a separate bowl combine flour, baking powder, and salt. Whisk together.
Add a small amount to the sugar mixture, alternating with milk mixing just until combined.
Toss blueberries with 1 tablespoon flour. Gently fold into the batter.
Carefully spread in the prepared pan.
Make the topping by combining the topping ingredients in a small bowl. Cut together with two forks or a pastry cutter.
Sprinkle over batter and bake 40-45 minutes or until a toothpick comes out clean.