Preheat oven to 350°F. Set glaze mix pouch aside. Combine cake mix, egg, water and butter and mix until batter is smooth. Stir in fresh blueberries. Spoon batter into prepared pan and spread evenly. Bake on center rack of oven for 55 to 60 minutes or until a toothpick inserted into center comes out clean. Remove from oven and cool in pan about 45 minutes. Remove cake from pan, place on wire rack set over sheets of wax paper.