Preheat your oven to 325 F. Line an 8x8 inch baking dish with parchment paper.
Combine the almond flour, melted butter, and granulated erythritol. Press evenly into the bottom of the dish. Bake for 10 minutes until lightly set.
Beat the softened cream cheese and powdered erythritol until smooth. Add the key lime juice, eggs, key lime zest, and vanilla extract. Mix until completely smooth.
Pour the filling over the warm crust and smooth the top with a spatula.
Bake for 25 to 30 minutes until the edges are set and the center has a very slight jiggle.
Let cool to room temperature, then refrigerate for at least 4 hours or overnight. Slice into bars and serve chilled, garnished with a dollop of whipped cream and extra lime zest if desired.
