Preheat oven to 350°F (180°C). Spray an 8-inch square baking pan with baking spray with flour. Line pan with parchment paper, letting excess extend over sides of pan.

In a medium bowl, whisk together flour, ginger, salt, baking soda, cinnamon, nutmeg, and cloves.

In a large bowl, whisk together brown sugar, molasses, melted butter, eggs, and vanilla. Whisk in flour mixture just until a few dry streaks remain. Whisk in ¾ cup (180 grams) hot water until combined. Pour batter into prepared pan.

Bake until a wooden pick inserted in center comes out clean, 45 to 50 minutes. Let cool in pan for 10 minutes. Using excess parchment as handles, remove from pan, and let cool completely on a wire rack. Just before serving, garnish with confectioners’ sugar, if desired. Store in an airtight container for up to 3 days.