Preheat the oven to 3250F and line a mini muffin pan with 24 silicone liners (or use a silicone mini muffin pan).

In a large bowl, whisk together the almond flour, sweetener, baking powder, and salt. Stir in the melted butter, egg white, and vanilla extract until the dough comes together.

Roll the dough into scant 1 inch balls and place in the prepared muffin cups. Bake 5 minutes in ball form, then remove from the oven and use a rounded teaspoon or another blunt rounded instrument to press a deep well into the center of each ball.

Bake another 10 to 12 minutes, until just browning lightly on the edges. Remove and let cool completely in the pan. If the wells in your cookies have puffed up a bit, reshape them when the cookies are still warm. Once cool, pop the cookie cups out of the silicone molds.