Preheat oven to 350°F (175°C). Line an 8x8 inch baking dish with parchment paper.
Make the crust: In a bowl, mix almond flour, coconut flour, melted coconut oil (or butter), maple syrup, vanilla, and salt until a dough forms.
Press dough into the bottom of the prepared pan and bake for 10–12 minutes, or until edges are golden. Let it cool slightly.
Make the filling: In another bowl, whisk together eggs, lemon juice, zest, sweetener, and coconut flour until smooth. Let rest for 5 minutes.
Pour filling over the pre-baked crust and return to oven. Bake for 18–20 minutes or until the center is just set and no longer jiggly.
Cool completely, then refrigerate for at least 1 hour before slicing into bars.
Dust with powdered sugar just before serving (optional but extra lovely). Enjoy chilled for best texture!