Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9 inch Bundt pan.
In a medium bowl, stir together the cake mix and instant pudding. Add the sour cream, oil and eggs, mix well. Pour half of the batter into the prepared pan. Combine the brown sugar, walnuts and cinnamon, sprinkle over the batter in the pan. Cover with the remaining batter.
Bake for 1 hour in the preheated oven, until cake springs back when lightly touched. Cool for 15 minutes in pan before inverting onto a wire rack to cool completely. When cake is cooled, dust with confectioners' sugar.