Gluten Free Cinnamon Streusel Breakfast Cake

I've been in the mood for breakfast cake for a few months now, but have had a hard time finding a recipe that I liked.  I wanted something simple with cinnamon so that my kitchen would smell like fresh baked cinnamon rolls without the effort or disappointment I've had from trying to bake them gluten free.  I also wanted a recipe using ingredients that I always have on hand so that I could make breakfast cake whenever the craving came. I ended up adding and subtracting things from a few recipes to come up with the following.  This creates a moist and delicious breakfast cake that our entire family loves!

Gluten Free Cinnamon Struesel Cake
Cake Batter:
1/2 cup sugar
2 teaspoons baking powder
1/2 teaspoon salt
3/4 teaspoon xanthum gum
1 teaspoon vanilla
2 eggs, beaten
1/2 cup buttermilk
1/4 cup vegetable oil

Cinnamon Streusel: (double if you want to put a layer of streusel in the middle of the cake**)
1/4 cup packed brown sugar
1 teaspoon ground cinnamon
1 tablespoon butter or margarine, melted

Combine the cake batter ingredients and mix well. Pour into a greased 9-inch square baking pan. Combine the dry streusel ingredients with the melted butter.  Sprinkle over the batter.  Bake at 375 degrees F for 30 minutes or until a toothpick inserted near the center comes out clean.  Serve warm. 
**For a sweeter breakfast cake, double the streusel topping and layer as follows: Spread half of the cake batter into the pan.  The layer will be thin.  Sprinkle half of the streusel over the batter and cover with the remaining batter.  Sprinkle the rest of the streusel on top.  Cook as directed above.