1 box yellow cake mix (2-layer size)
3/4 cup oil
4 large eggs
1 carton (8-oz) sour cream
1 cup brown sugar
1 tbsp ground cinnamon
2 cups powdered sugar
4 tbsp milk
1 tbsp vanilla extract
Preheat oven to 325 degrees.
Lightly spray a 9x13-inch baking pan with nonstick cooking spray; set aside.
In a mixing bowl beat the cake mix, oil, eggs, and sour cream by hand for 50 strokes. Pour half the batter into the baking pan.
In a small bowl, combine the brown sugar and cinnamon; spread over the batter in the pan. Pour remaining half of the batter over the sugar/cinnamon layer. Using a knife, make swirls in the cake.
Bake at 325 degrees for approximately 40 minutes until a wooden toothpick inserted in the center comes out clean.
In a bowl combine the powdered sugar, milk, and vanilla extract. Spread over the warm cake.