Preheat oven to 350˚F. Grease a 9x9-inch baking pan. Combine sugar and butter in a mixing bowl; cream together. Add egg and beat well. Sift together flour, baking powder, and salt. Add dry ingredients to creamed mixture alternately with milk, beating well after each addition. Fold in blueberries. Spread batter in prepared pan. Bake at 350˚F for 40 to 45 minutes or until top springs back when touched. Remove from oven and cool for 10 minutes, then remove from pan and place on wire rack.

To prepare Glaze:
In a bowl, cream together confectioner’s sugar, butter, and orange peel. Gradually stir in milk until mixture reaches desired consistency. Drizzle glaze over warm cake and serve.