Preheat your oven to 350°F (175°C). Line a 9×9-inch baking dish with parchment paper.
In a large bowl, mix together the melted butter and brown sugar until well combined. Add in the eggs, molasses, and vanilla extract, stirring until everything is fully incorporated.
In a separate medium bowl, whisk together the all-purpose flour, ground ginger, cinnamon, baking powder, and kosher salt until evenly distributed.
Gradually fold the dry ingredients into the wet mixture using a spatula or wooden spoon until just combined.
Spread the batter evenly into your prepared pan and place it in the preheated oven. Bake for about 30-35 minutes or until the edges are set and the center no longer jiggles.
Allow the brownies to cool completely in the pan before dusting with confectioners’ sugar. Cut into squares and serve.