Preheat the oven to 350° F. Line a baking sheet with parchment paper and lightly grease the paper.
In a mixing bowl, combine the almond flour, coconut flour, baking powder, xanthan gum, cinnamon and salt. Whisk until smooth and set aside.
In another bowl, beat the egg yolks together with 1/4 cup of the granulated allulose until it’s pale yellow. Beat in the pumpkin puree and vanilla.
In yet another bowl, beat the egg whites until soft peaks form. Add the remaining granulated sugar a little at a time until stiff peaks form.
Gently fold the two egg mixtures together, then add the flour mixture and fold in until well combined, being careful not to deflate the air bubbles.
Spread the mixture onto the prepared baking sheet. Bake for 15 minutes, or until the cake feels spongy to the touch. Remove it from the oven and let cool for 15 minutes.
Place a cutting board on top of the cake, flip it over carefully, and remove the parchment paper. Allow the cake to cool until it’s just barely warm.
While the cake is cooling, add the whipping cream, powdered sweetener, and vanilla extract to a bowl and beat until stiff peaks form. This works best when the whipping cream is very cold.
Spread the filling evenly over the cake. Carefully, roll the cake loosely into a log. Cover with plastic wrap and put it in the freezer to firm up, at least one hour.
Remove from the freezer about 10 minutes before serving. Remove the plastic wrap and dust the top of the roll with a bit of powdered sugar substitute. Slice to serve.