Prep the pan: Preheat your oven to 350°F (175°C). Line an 8x8-inch square baking pan with parchment, leaving an overhang on two sides for easy lifting.

Mix the crust: In a bowl, whisk almond flour, powdered sweetener, and salt. Stir in melted butter and vanilla until it looks like damp sand and clumps when pressed.

Press and bake: Firmly press the crust mixture into the pan in an even layer. Dock lightly with a fork. Bake 12–15 minutes, until the edges are just turning golden. Set aside.

Lower the oven: Reduce oven temperature to 325°F (165°C) so the filling bakes gently.

Make the filling: In a medium bowl, whisk eggs until smooth but not foamy. Whisk in granulated sweetener, lemon juice, lemon zest, almond flour, and salt until just combined and no lumps remain.

Pour and bake: Pour the filling over the warm crust. Tilt the pan to level. Bake 18–22 minutes, until the center is set but still slightly jiggly. It should not brown.

Cool completely: Let the pan cool on a rack to room temperature, then chill at least 2 hours. This helps the bars slice cleanly and the lemon flavor deepen.

Finish and serve: Lift out using the parchment. Dust with powdered sweetener if you like. Cut into 16 small squares or 9 larger bars. Serve chilled or at cool room temp.