This is a combination of a few recipes on the internet for key lime pie and biscoff cookie crust.
Process the cookies in a food processor. Melt the butter. Pour the melted butter in with the processed cookies and press into a pie pan. A glass pie pan works well here.
Bake at 350 for 10 minutes before filling.
Beat eggs on high speed until thick. Add condensed milk and beat at low speed. Stir in half the key lime juice, then add tartar, then the rest of the juice. Add a good pinch of salt.
Pour into pie crust, top with zest, and bake at 325 for 10-15 minutes. Refrigerate until cold and serve with whipped cream.