Sour Cream Coffee Cake

This recipe is from a Weight Watchers cook book.  I don't use fat free sour cream because I figure if you're going to use sour cream, you need to go big or go home! 

1 large egg
2 tbsp. canola oil
3/4 C. granulated sugar
1/2 C. sour cream
1/3 C. low fat buttermilk
2 1/3 C. all purpose flour
1 tbsp. baking powder
1/2 tsp. cinnamon or Chinese five spice powder
1 1/2 C. fresh blueberries
1/4 C. packed dark bron sugar
1 tsp. grated orange zest
2 tbsp. butter

Preheat the over to 350 degrees.  Spray a 7X11 inch baking dish with nonstick spray.

In a small bowl, combine the egg, oil and granulated sugar.  Whisk until pale yellow, then whisk in the sour cream and buttermilk.  In a large bowl, mix together 2 cups of the flour, the baking powder and the cinnamon.  Mix in the egg mixture.  Pour the batter into the baking dish, then scatter the blueberries on top.

In a small bowl, combine the brown sugar, orange zest, butter and the remaining 1/3 C. of flour.  Mix with the back  of a fork until crumbly, then sprinkle over the batter.  Bake until a tester inserted into the center of the cake comes out clean, about 45 minutes.  Cool slightly.