Meanwhile, heat heavy whipping cream and stevia over medium heat until hot but not quite boiling, stirring occasionally.
In a small bowl, combine monkfruit, almond flour, xanthan gum and salt. Add to heavy whipping cream mixture.
Stir often as it slightly thickens for about 5 minutes.
In a small bowl, beat egg yolks. Pour a small amount of hot mixture to egg bowl and stir vigorously to temper eggs. Pour egg mixture back into pot.
Continuously stir for about 5 minutes. It will begin to thicken.
Remove from heat and add vanilla and butter, stir to combine.
Add to pie crust, cover, and let cool in the fridge for 1 hour.