Preheat oven to 340F (170C).
Start with the crust: melt butter and mix with almond flour, egg, stevia, vanilla powder and cardamom until smooth.
Add dough to a pie pan and pre-bake for 10 minutes. Let cool.
Mix lemon zest and lemon juice together with eggs, cream, erythritol and stevia.
Pour mixture into the pie pan and bake for 20-30 minutes.