Preheat your oven to 350°F (175°C). Grease two 8-inch or 9-inch round cake pans and line the bottoms with parchment paper. This ensures your layers pop out easily after baking without any sticking.
In a large mixing bowl, whisk together the flour, ground ginger, cinnamon, cloves, baking soda, and salt. Make sure there are no lumps and the spices are evenly distributed throughout the flour mixture.
In a separate large bowl or a stand mixer, beat the softened butter and granulated sugar together on medium-high speed. Continue for about 3 minutes until the mixture looks light, fluffy, and pale in color.
Beat in the egg until fully combined. Pour in the molasses and mix well. The batter will look dark and glossy at this stage. Be sure to scrape down the sides of the bowl to ensure everything is incorporated.
With the mixer on low speed, add the dry flour mixture in three parts, alternating with the buttermilk in two parts. Begin and end with the flour. Mix only until just combined to avoid a tough cake.
Gently fold in the hot water by hand or on the lowest mixer setting. The batter will be thin, but this is normal! The hot water helps bloom the spices and creates a very tender, moist crumb.
Divide the batter evenly between the prepared pans. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.
Beat the softened cream cheese and butter together until smooth and creamy. Gradually add the powdered sugar, one cup at a time, followed by the vanilla extract and a pinch of salt. Beat on high for 2 minutes until light and airy.
Place one cooled cake layer on a serving plate. Spread a thick layer of frosting over the top. Place the second layer on top and cover the top and sides of the entire cake with the remaining frosting. Smooth with a spatula or leave it rustic with swirls.