Melt the butter then mix in the almonds and sweetener. Add the egg and mix again.
Line the bottom of your pie dish with baking paper, or grease with butter. Cover the dish with the pie base and spread out evenly
Bake at 180C/350F for 10 minutes, until just golden.
Heat the cream in a saucepan until just below boiling. Do not allow it to bubble. Remove from the heat.
In another bowl, whisk the eggs, egg yolks and sweetener together until pale and fluffy. Add the lemon zest and lemon juice. Stir through.
Slowly add a little of the warm cream to the egg mixture, constantly whisking all the time to stop the eggs from curdling or cooking. Keep adding the cream slowly until all mixed through. Put the filling back into the saucepan and heat gently until thickened.
Once it looks like lemon curd, and is as thick as custard, pour onto the pie base an bake at 180C/350F for 10 minutes.
Wipe around a large mixing bowl with kitchen paper to ensure it is free from any grease (which will stop the eggs whites from forming strong peaks). Add the egg whites, sweetener and vanilla and whisk until soft peaks form. Place on top of the pie base and lemon curd, put back in the oven at 180C/350F for another 10 - 15 minutes to allow the meringue to cook and go golden.