01 - Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
02 - Combine cranberries, erythritol, water, and orange zest in a small saucepan. Cook over medium heat for 5 to 8 minutes until cranberries burst and the mixture thickens. Mash lightly and set aside to cool.
03 - In a large bowl, whisk together almond flour, coconut flour, powdered erythritol, baking powder, and sea salt until evenly mixed.
04 - Add softened butter, egg, vanilla extract, and optional orange zest to dry ingredients. Mix thoroughly until a soft dough forms.
05 - Divide the dough into two equal portions. Roll each between two sheets of parchment paper into a rectangle approximately 6 millimeters (1/4 inch) thick.
06 - Spread half of the cooled cranberry mixture over each dough rectangle, leaving a small border around the edges.
07 - Carefully roll each rectangle jelly-roll style, then place in the freezer for 15 minutes to firm up.
08 - Using a sharp knife, slice each roll into cookies approximately 1.3 centimeters (1/2 inch) thick. Arrange cookies on the prepared baking sheet.
09 - Bake for 12 to 15 minutes or until edges are lightly golden. Allow to cool completely before serving.