Preheat an oven to 350°F (180°C) and line an 8″ x 8″ baking pan with parchment paper and grease with cooking spray.
In a large bowl, whisk together almond flour, erythritol+monk fruit mixture, salt, and unsweetened applesauce and stir to combine.
Press mixture into prepared pan in an even layer and bake until lightly golden for about 15 minutes. Set aside.
In another large bowl, combine eggs, fat-free Greek yogurt, lemon juice, lemon zest, and vanilla extract.
Add almond flour and erythritol+monk fruit mixture, and whisk to incorporate.
Pour filling over crust and bake until filling is set, 30-35 minutes.
Let cool to room temp, then refrigerate until set, about 2 hours. When ready to serve, cut into squares,
(optional) Dust with powdered erythritol / monk fruit mixture or other keto-friendly sweeteners