Honey Bun Cake

This is one of those no-fail cakes that everyone always asks for the recipe when I take it somewhere.
1 pkg yellow cake mix
3/4 cup vegetable oil
4 eggs
8 oz (1 cup) sour cream
3/4 cup brown sugar
1 Tbs cinnamon
Preheat oven to 325 degrees. In a large mixing bowl, combine cake mix, oil, eggs, and sour cream. Stir by hand approximately 50 strokes or until most large lumps are gone. Pour half of the batter into an ungreased 8x13 glass baking dish. (The original recipes says to make it in a glass dish, and I have never tried anything different.) Combine brown sugar and cinnamon and sprinkle over batter in the pan. Spoon the other half of the batter into the cake pan, covering the brown sugar and cinnamon the best you can. Twirl the cake with a knife until it looks like a honeybun or just make random swirls. Bake in a preheated oven 35 minutes or until done. Frost cake while it is still fairly hot.

Frosting for Honeybun Cake
2 cups confectioners sugar
4 Tbs milk
1 Tbs vanilla extract
Mix in a small bowl until smooth. Spread over hot cake