In a bowl, whisk together flour, baking powder and salt.
In a mixing bowl cream together butter, white sugar and light brown sugar on medium-high until fluffy, about 2 minutes.
Add eggs one a time. When well combined, alternate adding flour mixture and milk to batter. Mix just until combined.
Toss blueberries with 1 tablespoon flour, then fold them into the batter.
Preheat oven to 350 degrees.
Grease a 9×13 baking pan.
Pour batter into prepared pan and spread evenly. Sprinkle remaining 2 tablespoons sugar on top of cake batter.
Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.
Serve warm or at room temperature.
For Gluten Free Version use Bob's Red Mill 1 to 1 Gluten Free Flour Blend