Preheat oven to 350°Line an 8x8-inch baking dish with parchment paper.

Melt butter in a saucepan over medium heat. Once melted pour into a large bowl. Add the Swerve, vanilla extract, and egg yolk. Whisk until well combined.

Slowly add almond flour, coconut flour, and salt. Continue mixing until dough forms.

Press dough evenly into the bottom of the baking dish and bake for 20 minutes.

Allow cooling while you make the filling.

Beat together the eggs, lemon juice, lemon zest, and Swerve with an electric mixer.

Add arrowroot powder and mix until well combined.

Pour filling over crust and bake for 20 minutes or until the filling has set.

Allow to cool completely and refrigerate for 1 hour.

Slice into 16 bars and serve.