Mix cake mix, eggs, vegetable oil and sour cream in a large bowl with a mixer
Mix for 1 minute on low speed then 3 minutes on medium/high speed
Place in a greased tube pan and set aside
Mix together brown sugar and cinnamon in a small bowl and sprinkle on top of dough
Take a knife and swirl through the dough
Place in preheated oven and bake for 35-40 minutes or until toothpick tests done
Set on counter to cool and loosen sides with a knife
After 10 minutes remove from pan
After cooling completely, mix together frosting ingredients in small bowl and drizzling on topIf you need to put the frosting on before it is cooled completely, you certainly can. It just might melt a little bit. Still tastes great.
I do strongly suggest that the brown sugar is completely broken up (like in the picture above) before you sprinkle it on top of dough.