Preheat oven to 350°F.
Grease a 9-in square pan with nonstick cooking spray and set aside. I also like to line the pan with parchment paper that overflows on the side, as handles, for easy cake removal.
In a medium bowl, whisk together flour, baking soda, salt, ground ginger, ground cinnamon and ground cloves. Set aside.
Add butter, dark brown sugar, molasses and boiling water to a large bowl. Whisk until butter is fully melted. When the mixture is luke warm at touch, whisk in the egg until fully combined.
Add the dry ingredients to wet ingredients and whisk/fold until just combined and the batter has no lumps.
Transfer batter into the prepared pan and bake for about 35 minutes, check by inserting a toothpick into the center of the cake, it should come out with just a few cooked crumbs, not raw batter, the center of the cake should not be giggly.
Remove pan from oven place it on a rack to cool. You can serve the cake warm, without frosting, or wait for the cake to fully cool and frost.