In the bowl of a stand mixer, cream together the butter and sugar using the paddle attachment until light and fluffy, or about 3-5 minutes. Slowly add the egg, vanilla, and molasses, scraping down the sides as needed, then mix again on low.
In a medium bowl, sift together the flour, baking soda, salt, nutmeg, cinnamon, ginger, and cloves. Whisk together.
Add the hot water to the butter mixture and mix on low speed, then add the flour mixture to the butter mixture. Beat on low speed until combined, scraping down the sides of the bowl as needed.
Line a 9" x 9" baking dish with parchment paper, or spray with nonstick spray, then add the batter.
Bake in a preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and let cool to room temperature before frosting with buttercream. Enjoy!
Notes
Storing instructions: wrap any unfinished cake in aluminum foil or plastic wrap and store for up to 4 days in the refrigerator, or up to 2 months in the freezer.