Preheat oven to 325°F

Mix together cake mix, eggs, sour cream and oil by hand about 50 strokes.

In a separate bowl combine brown sugar and cinnamon. Set to the side

In a 9x13in pan add half of the cake batter then spread cinnamon mixture over the entire cake then spread remaining cake batter on top

Use a knife to make swirls in the cake

Bake for 40 minutes or until knife comes out clean. Let cake cool for about 30 minutes.

While cake is cooling, In a medium bowl mix together powdered sugar, vanilla extract, and milk. Spread over entire cake.