Preheat and prep: Heat the oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment, leaving overhang for easy lifting.

Make the crust: In a bowl, mix 1 1/2 cups almond flour, 2–3 tablespoons powdered sweetener, a pinch of sea salt, and 6 tablespoons melted butter. If the dough seems too soft, add 1–2 teaspoons coconut flour for extra structure.

Press and par-bake: Press the crust mixture evenly into the pan. Dock lightly with a fork. Bake 10–12 minutes until set and just barely golden at the edges. Let it cool for 5–10 minutes.

Whisk the filling: In a medium bowl, whisk 4 large eggs until smooth. Add 1/2 cup powdered sweetener, 1/2 cup fresh lemon juice, 1 tablespoon finely grated lemon zest, 1 teaspoon vanilla extract, a pinch of sea salt, and 1/3 cup heavy cream. Whisk until fully combined and slightly frothy.

Taste and adjust sweetness: Keto sweeteners vary. Dip a spoon in and taste. If too tart, add 1–2 more tablespoons sweetener. If too sweet, add a splash more lemon juice.

Pour and bake: Pour the filling over the warm crust. Reduce the oven to 325°F (165°C). Bake 18–24 minutes, until the center is mostly set with a slight jiggle. Do not overbake.

Cool and chill: Cool in the pan on a rack until room temperature. Refrigerate at least 2 hours, preferably 4, to fully set.

Slice and serve: Use the parchment to lift the slab out. Dust lightly with powdered sweetener if you like, then cut into 16 squares. Wipe the knife between cuts for clean edges.