Preheat oven to 350 degrees.
Crumb Topping: Mix flour, cinnamon, sugar and margarine together in a bowl with a fork until crumbly. Set aside.
Cake Batter: Oil and Flour a 8x8 pan. In a small bowl mix sliced apples with 2 tbsp brown sugar, set aside. Mix flour, baking powder, cinnamon and nutmeg together in a bowl, set aside. Cream butter and sugar until fluffy. Add egg one at a time, make sure each egg is well incorporated before adding another egg.
With the mixer on a low speed, alternately add flour mixture and apple cider to mixture, mix well. Add vanilla extract. Pour into prepared baking dish.
Place apple slices in one layer across the top of the batter. Sprinkle crumb topping evenly over apple slices.
Place into oven and bake for 50 mins.
Allow to cool before dusting with powdered sugar.