In a bowl, whisk together the buttermilk, eggs, and melted butter. Add the flour, sugar, baking powder, baking soda, and salt. Pour into a 9x11 inch baking sheet.
Place the strawberries, raspberries, and blackberries on top of the batter.
Bake in the preheated oven for 16-18 minutes or until a toothpick inserted into the center comes out clean and the edges are golden brown.
Let cool for 5 minutes before slicing and serving with powdered sugar and maple syrup if desired.