Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking dish with parchment paper.

Mix the melted butter and brown sugar in a large bowl until smooth, then add eggs, molasses, and vanilla and blend until glossy.

Whisk together flour, ground ginger, cinnamon, baking powder, and kosher salt in a medium bowl until combined.

Gradually stir the dry ingredients into the wet mixture, folding gently until just combined.

Pour the batter into the prepared baking dish and bake for 30 to 35 minutes until edges are set and the center jiggles slightly.

Allow the brownies to cool in the pan on a wire rack, then dust with confectioners' sugar and cut into squares.