Heat oven to 350F and prepare a 9x9 inch pan with oil or cooking spray. I line the bottom of the pan with parchment.
In a large mixing bowl combine the almond flour, coconut flour, sweetener, and lemon zest and stir until all ingredients are uniform.Mix the butter into the flour mixture. You can dig in with your hands to thoroughly incorporate the butter into the flour mixture if needed.
Press the dough into the prepared pan and bake for 15 minutes or until crust is golden. Set aside while you prepare the filling.
Bring a saucepan to low heat before adding butter, salt, erythritol, cardamom and almond milk. Stir until the butter and sweetener have been completely dissolved. DO NOT BOIL. Pour in lemon juice and zest.
Whisk eggs in a separate bowl.Slowly add to saucepan to temper while stirring continuously over low heat until the mixture begins to thicken.DO NOT BOIL...I REALLY MEAN IT. You'll end up with lumpy, lemony eggs. This should take about 10 minutes.Turn off heat and add vanilla. Whisk until it's incorporated.
Let cool to room temp before adding to crust. Put it in the fridge or freezer in a bowl to accomplish this faster if you are in a rush. If you leave it in the pan it will retain heat longer (but this is what I usually do to save dishes if I am not in a hurry).
Now is a good time to sample the lemon curd to make sure you didn't forget anything.
Transfer the lemon filling into your crust and return to the oven for 15 minutes. It will still be soft when it comes out and will continue to firm up as it cools.
Chill for one hour or until set before cutting & serving. Add powdered sweetener or other topping before serving if using.
Notes
The nutrition for this recipe is for 1 lemon square if you cut the total recipe into 12 squares.
Nutrition
Serving: 1square | Calories: 130kcal | Carbohydrates: 5g | Protein: 5g | Fat: 11g | Sodium: 79mg | Fiber: 2g | Net Carbs: 3g | Fat Ratio per Serving: 76.15% | Protein Ratio per Serving: 15.38% | Carb Ratio per Serving: 9.23%