Pre-heat the oven at 200 C.
For the crust, mix the almond flour, coconut flour, 2 tbsp. of butter, ½ tsp. of lemon zest and ½ cup of erythritol in a bowl. Add 2 tablespoons of water.
Spread cooking oil in a baking dish and pour the crust mix in it. Press it gently. Put it in the oven for 15 minutes or until crisp. Once it’s ready, take it out and let it sit.
In the meantime, you can prepare the filling – in a saucepan, put almond milk, 1 tbsp. of butter, the remaining ½ cup of erythritol and stir well until the erythritol is dissolved. Add the lemon juice and lemon zest and stir again.
Whisk the eggs in a bowl and slowly add them to the saucepan, by stirring continuously.
Stir until the mix starts to thicken (around 10 minutes).
Pour the filling mix on top of the crust and spread evenly. Cook in the oven for another 15 minutes.
In the meantime, you can prepare the topping – in a blender, put the coconut chips, sliced almonds and the remaining tablespoon of butter. Blend for about a minute.
Sprinkle the topping on top of the cake and bake for another 5 minutes.
Let the cake cool, cut into pieces and serve.