Breakfast Cake

My friend Tammy made this for us as a thank you.  It was delicious!!!!  I made it for us after I asked for the recipe, but it just wasn't the same (I used milk w/ vinegar to make buttermilk instead of using actual buttermilk).  She doubled this recipe so it fits in a 9x13.

Cake:
1/3 cup butter, softened
1/2 cup sugar
1/4 cup packed brown sugar
1 egg
1 cup flour
1/2 tsp baking powder
1/2 tsp ground cinnamon
1/2 cup buttermilk

Topping:
1/4 cup packed brown sugar
1/4 cup finely chopped walnuts
1/4 tsp ground cinnamon

Lightly grease an 8" square baking pan.  In a bowl, combine, butter and sugars.  Add egg.  Combine dry ingredients in a separate bowl.  Stir the flour mixture into the creamed mixture alternately with the buttermilk.  Spread evenly into baking pan.

In a small bowl, combine the topping ingredients.  Sprinkle over the batter.  Cover, and refrigerate overnight.

The next morning, preheat oven to 350 degrees.  Bake the cake for 40-45 minutes in the oven or until a toothpick comes out clean.  (Less cooked is better.)