1 box yellow cake mix
3/4 c. oil
4 eggs
8 oz. sour cream
1 tbsp. cinnamon
1 c. brown sugar

Mix first 4 ingredients by hand. Pour 1/2 the batter in greased 9x13 pan. Set other 1/2 batter aside. Mix together cinnamon and brown sugar. Sprinkle over first layer of batter. Pour remaining 1/2 of batter over top of all. Bake at 325 for 40 minutes.

ICING:

2 c. powdered sugar
4 tbsp. milk
1 tsp. vanilla

Mix all ingredients. Pour over cake as soon as it comes out of the oven.