Heat oven to 350 degrees. In a small bowl, combine flour, baking powder, and salt, and set aside. In a medium bowl, cream together butter and sugar. Beat in egg. Stir in flour mixture, a third at a time, alternating with milk (beginning and ending with flour mixture).
In a medium bowl, combine apples, sugar, cinnamon, and ginger, and place in an ungreased two-quart casserole dish. Pour batter over apple mixture; make sure all apple pieces are covered.
In a medium saucepan over high heat, combine cider and maple syrup and bring to a boil, stirring often. Pour over batter; it will sink. Bake 35 to 45 minutes, or until a toothpick inserted into the center of the cake (without hitting the liquid on the bottom) comes out clean.