Updated from myhomemdelife.blogspot.com
1 yellow cake mix
1 cup brown sugar
2 cups powdered sugar
3/4 cup oil
1 Tablespoon cinnamon
4 Tablespoons milk
1 Tablespoon vanilla extract
8 oz sour cream
Mix cake mix, oil, eggs, and sour cream by hand, about 50 strokes.
Put half the batter in 9 x 13 pan.
Combine brown sugar and cinnamon and spread over entire cake. Spread the rest of the batter on top of this.
Use a knife to make swirls in the cake.
Bake at 325 degrees for about 40 minutes.
Blend powdered sugar, milk and vanilla extract and spread on warm cake.