Preheat oven to 350°F.
Line baking sheets with parchment paper.
Whisk flour, baking powder, baking soda, spices, and salt.
Cream butter and brown sugar until fluffy.
Beat in egg, vanilla, cider, and applesauce.
Gradually add dry ingredients to wet mixture.
Mix until just combined.
Drop batter by tablespoons onto prepared sheets.
Bake for 10 minutes or until set.
Cool completely on a wire rack.
Beat filling ingredients until creamy.
Spread filling on flat side of one cake.
Top with another cake to make a sandwich.
Repeat for remaining cakes.