Preheat the oven to 350°F (175°C). In a mixing bowl, combine almond flour, coconut flour, 1/2 cup of granulated sugar, and salt. Mix well. Pour in melted butter and stir until crumbly. Press the mixture into the bottom of a baking dish and bake for 15 minutes until golden brown.
In a separate bowl, whisk together the eggs, 1 cup of granulated sugar, fresh lemon juice, lemon zest, and baking powder until smooth. Set aside until the crust is done baking.
Pour the lemon filling over the baked crust and return to the oven. Bake for an additional 20-25 minutes until the filling is set and slightly firm to the touch.
Let the bars cool completely in the pan on a wire rack. Refrigerate for at least 1 hour before slicing. Dust with powdered sugar before serving.