Get Ready: Preheat your oven to 350°F (175°C). Line an 8x8 inch baking pan with parchment paper, letting it hang over the sides for easy lifting, then lightly grease it.
Whip up the Crust: In a stand mixer (or a large bowl with an electric mixer), beat the softened cream cheese until smooth. Scrape down the bowl, then add the almond flour, heavy cream powder, coconut flour, egg, egg yolk, sweetener, and salt. Mix until everything is well combined and the dough starts to pull away from the sides of the bowl. It will be a soft dough.
Press and Bake the Crust: Evenly press the crust dough into the bottom of your prepared baking pan. Bake for 10 minutes until lightly set.
Prepare the Zesty Filling: While the crust bakes, combine all the filling ingredients – the finely ground sweetener, softened butter, heavy cream, eggs, softened cream cheese, fresh lemon juice, and lemon zest – in your stand mixer. Beat until completely smooth and creamy.
Assemble and Bake: Carefully pour the lemon filling over the warm, pre-baked crust. Return the pan to the oven and bake for 30-35 minutes, or until the filling no longer jiggles when you gently shake the pan.
Cool and Chill: Let the lemon bars cool completely at room temperature. For the neatest slices, chill them in the refrigerator for at least 2-3 hours.
Slice and Serve: Use the parchment paper overhang to lift the entire batch of bars out of the pan. Cut into 16 squares. If you like, dust with a little extra powdered keto-friendly sweetener right before serving for a beautiful finish!