Berry Crumbcake Bars

6 T unsalted butter, melted ½ C butter room temp., plus more for greasing pan ½ t baking powder 1 C confectioners sugar ½ t pure vanilla extract 1 ¾ C all-purpose flour, plus more for pan 2 large eggs 2 cups of any fresh berries (if frozen, thaw and drain first) ½ C...