Pour your melted butter in a 12 x 8 rectangular baking pan and set aside.
In another bowl, mix together flour, baking powder, salt, sugar and milk.
Pour the batter into your buttered pan and spread out evenly with a spatula.
Place your blackberries, one by one, on top of the batter (avoid getting liquid onto the batter as much as possible).
I think this dessert is best served warm with some vanilla ice cream! I hope you enjoy it, let me know how it turns out for you in the comments! Enjoy!