Preheat oven to 350°F. Mix flour, cocoa powder, ginger, baking powder, baking soda and cinnamon in medium bowl. Set aside.
Beat butter, sugar and molasses in large bowl with electric mixer on medium speed until well blended. Mix in egg. Add flour mixture alternately with water, stirring just until mixed. Pour into greased 9-inch square baking pan.
Bake 40 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack 10 minutes. Invert cake onto wire rack to cool completely.