Preheat the oven to 350°F.
Melt the butter in a medium bowl, then mix in the cake mix until you have a thick batter.
Add frozen blueberries to a baking dish, then drop the cake batter on top and spread evenly.
Bake for 45-55 minutes, or until the edges are golden brown and the center is set.
Allow to cool for 10 minutes and enjoy with vanilla ice cream.