Spray a 23 cm layer cake pan with cooking spray. Add brown sugar, corn syrup and lemon juice together; stir to combine. Put in pan. Place pan in 350 degree oven 3 minutes. Remove. Add blueberries. Prepare White Cake batter. For the cake batter: In a large bowl, combine flour, cornstarch, baking powder and salt. In a medium bowl, using a fork or wire whisk, mix egg, milk, corn syrup and vanilla. Add to flour mixture; stir until smooth. Carefully spoon batter over blueberries, smoothing top. Bake 35 to 40 minutes at 180ºC or until a toothpick inserted in center comes out clean. (Do not underbake) Immediately run a spatula around edge of pan, and invert onto a serving plate. Makes dozen servings.