Jam (Era Fulbright Coffman Waters) made this wonderful cake whenever the family got together and is a great favorite of many of her grandkids and great-grandkids.
In a large bowl:
1 pkg Duncan Hines Butter Recipe cake mix
4 eggs
2/3 c. Wesson oil
1t. vanilla
1 8oz. carton sour cream
In extra bowl put:
2 T. cinnamon
5 T. sugar
Mix ingredients in extra bowl and set aside. Mix batter in large bowl, put about half of batter in greased and floured tube pan (line tube pan with brown paper and butter). Sprinkle 3 T. sugar and cinnamon mixture onto batter in pan. Stir with fork to marbleize. Pour in remaining batter. Sprinkle remaining mixture, withholding a small amount for top, and marbleize. Bake at 350º for 45 minutes to 1 hr. Check with icepick or skewer at 45 min.