Preheat oven to 325°F (160°C). Line a baking sheet with parchment paper. In a medium bowl, combine the chopped pecans, almond flour, coconut flour, baking powder, and salt. Whisk briefly to combine.
In a large bowl, using an electric mixer, beat the softened butter, brown sugar replacement, and softened cream cheese until light and fluffy. This should take 2-3 minutes.
Beat in the egg and vanilla extract until well combined, scraping down the sides of the bowl as needed.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix. The dough will be soft.
Roll rounded tablespoons of dough into crescent shapes and place them on the prepared baking sheet, spacing them about 1 inch apart.
Bake for 12-15 minutes, or until the edges are lightly golden and the centers are set. The cookies will be very soft when hot.
Let the cookies cool on the baking sheet for 5 minutes before carefully transferring them to a wire rack to cool completely. They will firm up as they cool.