In a medium bowl, whisk together flour, cinnamon, ginger, baking soda and nutmeg. In a large bowl, beat butter until creamy. Beat in brown sugar and maple syrup. Beat in eggs (mixture will look slightly curdled). On low speed, beat in half the flour mixture, then the sour cream mixture and ending with the remaining flour mixture. Stir in maple flavoring. Transfer to prepared pan and spread level. Bake at 350 degrees for 30 minutes, or until toothpick inserted in center of cake tests clean. Cool in pan for 5 minutes on wire rack. Remove from pan and remove wax paper. Cool completely.