Heat oven to 350 degrees F (175 degrees C). Coat a Bundt pan well with cooking spray.
Make the streusel topping: Mix 1 brown cup sugar, 2/3 cup flour, and cinnamon in a medium bowl. Cut in 1/2 cup butter or margarine; topping mixture will be crumbly. Set aside.
For the cake: Beat 1/2 cup butter or margarine in large bowl until creamy; add 1 cup white sugar, and beat until fluffy. Beat in egg and vanilla. Whisk together 2 cups flour, baking powder, and salt; add alternately with the milk to the creamed mixture, beating well after each addition.
Spread half the batter in the prepared pan. Cover with berries, and add remaining batter by tablespoons. Cover with streusel topping.
Bake at 350 degrees F (175 degrees C) for 55 to 60 minutes, until deep golden brown. Remove pan to wire rack to cool. Invert onto a plate after cake has cooled, and dust with confectioners’ sugar.