Preheat oven to 350°F. Grease and flour a 9 inch bundt pan. Cream the butter and sugar then add one egg at a time, stir in the sour cream and vanilla. Combine the flour, baking powder and stir into batter until blended. Fold in blueberries. Combine brown sugar and cinnamon separately. Spoon 1/2 the batter into pan. Sprinkle 1/2 the brown sugar and cinnamon mixture then layer the remainding batter and sugar mixture. Bake for 60 min. or until a knife comes out clean. Dust with icing sugar when cooled if desired. Recipe adjusts well with Greek yogurt instead of sour cream, sugar substitutes for sugars or mix your berries with raspberries.