Honeybun Cake

1 pkg. yellow cake mix
¾ c. vegetable oil
4 eggs
1 8 oz. sour cream
1 c. brown sugar
1 T. cinnamon
2 c. powdered sugar
4 T. milk
1 T. vanilla

Preheat oven to 325 degrees. Combine mix, oil, eggs & sour cream. Stir about 50 strokes. Pour ½ of batter into ungreased 9x13 pan. Combine brown sugar & cinnamon. Sprinkle over batter. Cover with rest of batter. Twirl cake with knife to marble. Bake for 40 minutes. Frost cake while still hot. Serve warm or eat cold!