Procedure:

1. Preheat oven to 325°F.
2. Combine cake mix, oil, eggs, and sour cream.
3. Stir by hand until most large lumps are gone.
4. Pour half of the batter into an ungreased 9" x 13" glass baking dish.
5. Combine the brown sugar and cinnamon, and sprinkle over the batter in the cake pan.
6. Spoon the other half of the batter into the cake pan, covering the brown sugar and cinnamon.
7. Twirl the cake with a butter knife until it looks like a honey bun.
8. Bake for 40 minutes, or til a toothpick inserted into the center comes out clean.
9. Frost cake while it is still fairly hot.

Frosting:
Whisk together the confectioners sugar, milk, and vanilla extract til smooth.

The recipe says to serve this cake warm....and that would be pretty darned heavenly I can imagine! But I always have served it later after it's cool and it's good enough to please then, too.