Grease and flour a bundt or tube pan; Set aside. Preheat the oven to 350 degrees F.
Cream butter and sugar together in a large bowl until light and fluffy. Add in the eggs one at a time, mixing until yolk disappears, then the vanilla.
In a separate bowl, whisk together flour, powder, baking soda, and salt. Add to cream mixture alternating with the sour cream until well combined.
In a small bowl combine brown sugar, flour, and cinnamon; Set aside.
Pour a third of the batter into prepared baking pan, spreading evenly.
Sprinkle half of the brown sugar mixture over the batter in in the pan. Place half of the blueberries on top. Repeat layers then top with the remaining batter.
Bake until cake tester inserted in the center comes out clean, about 55-65 minutes or until. Allow cake to cool in the pan, set on a wire baking rack for 10 minutes. Remove from pan and let cool completely on wire baking rack.
Meanwhile, prepare the glaze.
In a medium mixing bowl, whisk the powdered sugar and 2 tablespoons of milk together until smooth. Add more milk as necessary to obtain a pouring consistency. Drizzle glaze over cooled coffee cake. Garnish with fresh blueberries.