Generously grease and flour a 10-inch bundt pan.
Preheat oven to 350°.
Mix flour with baking powder, soda and salt 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 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.
Bake 60 minutes, or until knife inserted in center comes out clean.
Cool in pan on wire rack 20 minutes.
Gently remove from pan.
Mix powdered sugar and milk until smooth; drizzle over cake.