Lowfat Blueberry Crumb Cake

Ingredients:
Vegetable oil spray
1 1/2 cup all purpose flour
3/4 cup light brown sugar
1/2 cup cake flour
1/2 teaspoon of salt
1/2 teaspoon baking powder
1/4 teaspoon baking soda
1 teaspoon cinnamon
4 tablespoon unsalted butter
1/2 cup of sugar
2 eggs (room temperature)
3/4 cup low fat yogurt
1 teaspoon vanilla
1 1/2 cup fresh/ frozen blueberry (if frozen, do not thaw), tossed with 1 tablespoon of flour

Direction:
Preheat oven to 350 degrees. Line 8 x 8 baking pan with foil. Spray the foil with vegetable oil spray.
In a  medium size bowl, whisk 1/2 cup of brown sugar, flour, cake flour, baking powder, baking soda, and salt together. Take 1/4 cup of the flour mixture, and transfer to a smaller bowl and mix in the remaining of the brown sugar. Melt 1 tablespoon of butter, let it cool slightly, add to the brown sugar mixture. Tossed until it formed pea-sized crumble. Set aside.
Cream butter and sugar with an electric mixer (medium-high speed) until light and fluffy (3-5 minutes). Add eggs one at the time, then the vanilla. Mix well until blended (30 seconds). Lower the speed. Add 1/3 of the flour mixture, alternate with 1/4 cup of yogurt. Repeat until all the flour and yogurt are mix well. Turn of the mixer, fold the blueberries. Pour the batter to 8x8 baking pan. Sprinkle the brown sugar mixture to the top of the batter.
Bake 35-40 minutes until the top and golden brown. Check using toothpick.