Preheat oven to 350 degrees F. In a large bowl, combine the cake mix and melted butter. Mix until you have a crumbly texture. Spray the bottom of a 9x13 pan with cooking spray.
Spread the blueberry pie filling evenly in the pan. Add 1 cup of fresh blueberries (optional), followed by the cake mixture. Top with a few additional fresh blueberries, if desired.
Spraythe top of my cake with a bit of cooking spray to moisten the top of the cake a little more. (This helps the top to get a golden brown color. - This is not required)
Bake for approximately 30-35 minutes, or until golden brown and bubbly. Carefully remove from the oven, let cool, add scoop of vanilla ice cream on top of each serving (optional) and enjoy.