Cinnamon Streusel Cake

I'm going to start with my son's favorite dessert right now since I have made this at least once a week this past month! He loves what he calls "cinnamon cake"! The past few months I have tried many coffee cake recipes that have ended in disappointment- none were just quite right. So, I decided to experiment with combining elements from different recipes. The result is a very moist cake with a hint of yummy gooey cinnamon in the middle and a yummy streusel topping. My family has declared this one a definite winner! Enjoy!

Cake
1 1/2 cups all purpose flour
1 tsp baking soda
1 tsp baking powder
1/2 tsp salt
2 eggs
1/2 cup butter
1 cup white sugar
1/2 tsp vanilla
1 cup sour cream

Filling
1/2 cups packed brown sugar
1 tsp cinnamon

Streusel topping
1/2 cup white sugar
2 tbsp flour
3/4 tsp cinnamon
2 tbsp cold butter

Preheat oven to 350 degrees. Grease and flour a 9 inch square baking pan. Mix together flour, baking powder, baking soda and salt. Set aside.
In another bowl, cream together sugar, eggs, butter and vanilla. Slowly beat in the flour mixture and sour cream, alternating. Spoon half of the batter into the pan. Mix the brown sugar and cinnamon for the filling and sprinkle over the batter. Spoon the remaining batter over the filling (this won't be smooth- just dollop it on until you run out).
Combine the sugar, flour and cinnamon for the streusel topping. Cut in the cold butter with a pastry blender (or I use my hands) until it is about pea sized. Sprinkle topping evenly over batter.
Bake for 35-45 minutes or until a toothpick comes out clean.