Preheat oven to 350°F 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. The batter will be thick. Spoon half of the batter into the prepared pan. Combine the brown sugar, pistachios and cinnamon, sprinkle over the batter in the pan., being careful to keep filling from the edges as it might stick to the pan. Cover with the remaining batter.
Bake 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 powdered sugar.