Preheat oven to 350°F, grease two whoopie pie pans, and set aside.
In a large bowl, combine almond flour, sweetener, pumpkin pie spice, baking powder, and salt.
Add eggs, pumpkin purée, and vanilla extract, and mix until well combined.
Add melted butter and water and mix again.
Use a cookie scoop to fill each cavity of the whoopie pie pans. Smooth the batter using an offset spatula.
Bake for 10-13 minutes until light brown and set.
Allow the cakes to cool completely (approximately 45 minutes) on a wire rack.
To make the filling, whip the heavy cream on high speed until it begins to stiffen. Slowly add powdered sweetener and whip until firm.
In separate bowl, whip the cream cheese until light and fluffy. Add the cream cheese to whipped cream and use the mixer to whisk for 30 seconds until just combined.
Use a piping bag or Ziploc bag with a corner cut off to pipe the filling on top of 12 of the cakes. Top each cake with remaining cakes to close the pies.