Heat your oven to 350°F (175°C).
Grease baking pan with butter.
Line with parchment paper.
Mix flour, ginger, cinnamon, nutmeg, and baking soda.
Set dry ingredients aside.
Beat butter and brown sugar until fluffy.
Add molasses and egg, mixing well.
Gradually add flour mixture to butter mixture.
Slowly pour in warm water.
Mix until smooth batter forms.
Pour batter into prepared baking pan.
Spread evenly with spatula.
Bake for 25-30 minutes.
Test with toothpick for doneness.
Cool completely before cutting.