Preheat oven to 350° and line a large baking sheet with parchment paper.  In a medium bowl, using a whisk or hand mixer, cream together butter and Swerve until light and fluffy. Add in peanut butter and whisk until completely incorporated. Whisk in yolk until fully combined. Fold in almond flour, coconut flour, and salt and mix until dough slightly stiffens. Using a small cookie scoop, scoop dough onto prepared sheet 1” apart. Sprinkle cookies with more salt and pecans. Bake until bottoms are deeply golden, about 11 minutes. Cool completely before serving.