01 - Preheat the oven to 350°F. Grease a 9-inch square baking pan and line it with parchment paper.
02 - Whisk together the flour, ground ginger, cinnamon, cloves, nutmeg, salt, and baking soda in a medium bowl.
03 - In a large bowl, beat the softened butter and brown sugar together until light and fluffy.
04 - Add the egg to the butter mixture and beat until combined, then mix in the molasses until smooth.
05 - Add the dry ingredients to the wet mixture in two parts, alternating with half of the hot water each time; mix gently until just incorporated.
06 - Pour the batter into the prepared pan, smoothing the surface evenly. Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.
07 - Let the cake cool in the pan for 10 minutes. Then transfer it to a wire rack to cool completely.
08 - Serve plain or dusted with powdered sugar as desired.