Preheat the oven to 350°F (175°C).
In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In another bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the eggs, apple cider, and vanilla extract to the creamed mixture, and mix until fully combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Drop tablespoons of dough onto a lined baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 12-15 minutes, or until the edges are lightly golden.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Once cooled, spread caramel sauce on the flat side of one cookie and sandwich it with another cookie.
Serve and enjoy your delicious apple cider whoopie pie cookies!