Generously grease and flour a 10-inch bundt pan.
Preheat oven to 350°.
Mix flour with baking powder, soda and salt in a mixing bowl and set aside.
In small bowl, combine brown sugar with 1 tbsp. flour and cinnamon; mix well.
In a large bowl of electric mixer, at medium speed, beat butter with granulated sugar and vanilla until fluffy.
Add eggs, one at a time, beating after each addition.
At Low speed, beat in flour mixture (in three additions) alternately with sour cream (in two additions) beating until combined.
Turn one-third of batter into prepared pan, spreading evenly.
Sprinkle with half the blueberries and half the brown sugar mixture.
Repeat layering of remaining batter, blueberries and brown sugar mixture.
The top layer should be batter.
Bake 60 minutes, or until knife or bamboo skewer inserted in center comes out clean.
Cool in pan on wire rack 20 minutes.
Gently remove from pan.
Mix powdered sugar and milk and whisk until smooth; drizzle over cooled cake.