Preheat oven to 350 degrees F. and spray a bundt cake pan generously with cooking spray.
Place cake mix, pudding mix, eggs, milk, oil and sour cream into a large mixing bowl. Mix until well combined. Transfer half of the cake batter into the bundt cake pan. Combine brown sugar and cinnamon into a medium bowl, stirring to combine. Pour evenly over cake batter in bundt cake pan. Spoon remaining cake batter over cinnamon sugar layer, spreading carefully. Bake for 35-40 minutes, until cake is baked through. Check center with a toothpick to assure it comes clean. Remove cake and take a plastic knife around edges to loosen while it cools. When cool, carefully flip cake onto cake plate. If any cake gets left in pan, carefully remove it and patch it back onto cake. Frosting will cover it :)
To prepare frosting place cream cheese and butter into a mixing bowl, stir until well combined then slowly add powdered sugar until nice thick consistency. Continue adding powdered sugar until needed. Either spread over cooled cake, or place frosting in a piping bag with a large round tip and pipe frosting lines that go from inside to outside of cake as shown in my photos.