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

In a large mixing bowl, combine melted butter and brown sugar until smooth. Add eggs, molasses, and vanilla extract and mix until creamy.

In a separate bowl, whisk together flour, ground ginger, cinnamon, baking powder, and kosher salt.

Slowly add the dry ingredients to the wet mixture, folding gently until just combined.

Pour the batter into the prepared baking dish and smooth the top.

Bake for 30-35 minutes until edges are set and center jiggles slightly. A toothpick should come out with moist crumbs.

Allow to cool in the pan for 10 minutes, then lift out using the parchment paper to cool completely on a wire rack.

Dust with confectioners' sugar, slice into squares, and serve warm or at room temperature.