Preheat the oven to 350°F and grease a loaf pan. Combine the almond flour, coconut flour, sugar-free sweetener, baking powder, pumpkin pie spice, and salt in a bowl and whisk well.
In a food processor, combine the pumpkin, butter, heavy cream, and eggs then blend smooth.
Whisk the wet ingredients into the dry mix then fold in the walnuts.
Pour the batter into the pan and bake for 55 to 65 minutes until a knife inserted in the center comes out clean.
Turn off the oven and let the loaf cool for 15 minutes.
Remove the loaf and turn it out onto a wire rack to cool completely then cut into 12 slices.