Preheat the oven to 180 ° C.
In a saucepan, melt the butter until a nutty odor is obtained, then set aside.
In a bowl, pour the almond flour and erythritol. Add the hazelnut butter then mix until obtaining a crumbly mixture but which holds when press.
In a 24 cm round pan, cover the bottom with parchment paper then pour the shortbread. Press until a flat and homogeneous surface is obtained.
Boil the lemon juice with the zest in a saucepan.
In a bowl, mix the eggs and erythritol with an electric mixer until a clear and frothy mixture is obtained.
Drizzle the lemon juice over the mixture while continuing to mix.
Return to a saucepan and mix with a whisk until the mixture thickens.
If the mixture does not thicken, you can add a tablespoon of cornstarch or a teaspoon of xanthan gum.
Remove from the heat and add the soft butter. Mix well and let cool a bit.
Pour the mixture on the shortbread base and place in the fridge until cool or until the jelly sets.
In a bowl, beat the egg whites with a pinch of salt until stiff.
Gradually add the powdered erythritol and beat until the meringue is obtained.
On the cold lemon cream, place the meringue according to your imagination (pastry bag, spiral ...)
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.