01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a medium mixing bowl, whisk together almond flour, coconut flour, baking powder, and sea salt until evenly combined.
03 - In a large bowl, beat softened butter with granulated erythritol using an electric mixer until mixture is light and creamy. Add egg and vanilla extract, mixing until smooth.
04 - Gradually stir dry ingredients into wet mixture until a cohesive, soft dough forms.
05 - In a small bowl, blend almond butter with powdered erythritol if desired for extra sweetness.
06 - Portion dough into tablespoon-sized balls using a spoon. Arrange balls 2 inches apart on prepared baking sheet.
07 - Gently flatten each dough ball. Place 1/2 teaspoon almond butter mixture on top of each cookie, then use a toothpick or skewer to swirl into the dough and create a marbled effect.
08 - Bake for 10 to 12 minutes, until the edges are lightly golden while centers remain soft.
09 - Leave cookies on baking sheet for 10 minutes to firm up, then transfer to a wire rack to cool completely.