Preheat oven to 350 F. Grease and flour a 9-inch square metal baking pan.
In a large bowl, stir together the butter and sugar.
Stir in the molasses.
Mix in the egg.
In a separate medium bowl, sift together the flour, baking soda, salt, cinnamon, ginger, cloves, allspice, and nutmeg.
Stir the dry ingredients into the molasses mixture until just combined. Batter will be thick.
Mix in the hot water.
Pour into the prepared pan.
Bake 30-40 minutes, or until a wooden toothpick inserted in the center comes out clean.
Let cool in pan before serving.
Notes
Butter: I use salted butter in this recipe. Feel free to use unsalted if you prefer. Also, the butter should be just melted, about 40 seconds in the microwave, not hot and sizzling.
Brown sugar: You can use light or dark brown sugar in this recipe. If you like your gingerbread sweeter, increase brown sugar up to 1 cup.
Molasses: I use a robust molasses in this recipe because I like a stronger molasses flavor. You can use mild or regular molasses if you prefer. I don't recommend blackstrap molasses in this recipe as it can be bitter.
Flour: To properly measure the flour either weight it or stir or sift to break up the flour, lightly spoon into the measuring cup, and level. Avoid packing in the flour.
Spices: If you prefer your gingerbread on the spicier side, double or triple the spices and throw in a pinch of ground pepper.
Hot water: I use hot tap water. I don't boil the water.
Baking pan: If you use a glass baking dish, you will need to turn the oven down by 25F and start checking for doneness about 5 minutes before the stated time.