Preheat oven to 350°F. Grease a 9x9-inch baking dish with cooking spray or butter.
In a large bowl, cream together ½ cup butter and ½ cup sugar until light and fluffy, using either a hand mixer or a stand mixer.
Beat in 2 eggs, one at a time, and then beat in 1 cup unsulphured molasses.
Whisk the dry ingredients (2½ cups all-purpose flour, 1 teaspoon salt, 2 teaspoons baking powder, ½ teaspoon baking soda, 2 teaspoons ground cinnamon, 1 teaspoon ground ginger, and ½ teaspoon ground cloves) in a medium bowl until combined.
Stir half the flour mixture into the butter/sugar mixture, then HALF of the 1 cup hot water. Repeat with the remaining flour mixture and remaining water.
Pour the batter into the greased pan. Bake for 40–45 minutes, or until a toothpick inserted into the center comes out with dry crumbs. Let cool completely.
For the whipped cream, place the 1 cup heavy cream, 1 tablespoon powdered sugar, and ½ teaspoon vanilla extract in a large bowl. Mix with a hand mixer or in a stand mixer until soft peaks form.
Cover and refrigerate the whipped cream until you’re ready to serve the cake, then dollop on top of the cake.
Notes
Unsulphured molasses is the best choice for this recipe. I used Grandma's brand (see photo above in the "Ingredients" section). Unsulphured molasses is not the same as blackstrap molasses. Blackstrap molasses is stronger and more bitter, which will overpower the cake. If you forget to take the butter out to soften, follow these instructions for how to soften butter quickly.Do NOT use an 8x8-inch pan, the batter will overflow. Use a 9x9-inch square pan, or an equivalent. Make it ahead: you can make the cake and whipped cream a day in advance. Keep the cake covered at room temperature and the whipped cream in the fridge. The cake can also be frozen, tightly wrapped, for a month or two.