Preheat oven to 350°F. Butter a 9-inch cake pan. In a mixing bowl, combine sugar and butter; with an electric beater, beat until well blended. Add flour, baking powder and eggs; beat until combined. Spread batter in the prepared pan. Sprinke blueberries evenly over batter. Bake until cake pulls away from the sides of the pan and is golden, about 1 hour. Cool on a rack for 10 minutes. Turn out onto cake plate, blueberry side up. In a small bowl, combine confectioners sugar with milk; drizzle mixture over blueberries.