Preheat oven to 350°F and line a baking sheet with parchment paper or a silicone mat.
In a mixing bowl, combine almond flour, coconut flour, erythritol, and baking powder; mix well using a spoon.
Cut in the butter and vanilla and work it with your fingers until a dough forms.
Use your hands to roll the dough into 12 equal balls. Place the balls 2-inches apart on prepared baking sheet. Use a fork to flatten and create a striped pattern.
Bake the cookies for 11-14 minutes, or until browned around the edges. Transfer to wire rack to cool.
Best stored in an air tight container or zip top bag in the fridge up to 10 days.