Preheat the oven to 350°F. Grease and flour a 9” Bundt pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the sour cream and vanilla. Combine the flour, baking powder, and salt; stir into the batter just until blended. Fold in blueberries. Spoon half of the batter into the prepared pan.
In a small bowl, stir together the brown sugar, cinnamon and pecans. Sprinkle half of this mixture over the batter in the pan. Spoon remaining batter over the top, and then sprinkle the remaining pecan mixture over.
Use a knife or thin spatula to swirl the sugar layer into the cake.
Bake for 55 to 60 minutes in the preheated oven, or until a knife inserted into the crown of the cake comes out clean. Cool the pan over a wire rack.
Invert onto a serving plate, and tap firmly to remove from the pan. Dust with confectioners’ sugar just before serving.