Preheat oven to 350°F (175°C). In a food processor, pulse pistachios until finely ground. In a bowl, combine ground pistachios, melted butter, sugar, flour, and salt. Mix until crumbly. Press mixture into a pie dish evenly. Bake for 10-12 minutes until lightly golden. Allow to cool.

Lemon Filling

Make the Lemon Filling

In a saucepan, whisk together sugar, cornstarch, and water. Cook over medium heat until thickened, stirring constantly. In a separate bowl, whisk egg yolks and slowly add some hot mixture to temper them. Pour egg yolk mixture back into the saucepan. Stir in lemon juice, lemon zest, and butter. Cook until thick, about 2-3 minutes. Pour filling into the cooled crust.

Meringue Topping

Prepare the Meringue

In a clean bowl, beat egg whites with an electric mixer until soft peaks form. Gradually add sugar and cream of tartar, beating until stiff peaks form. Spread meringue over lemon filling, sealing the edges.

Baking and Serving

Bake and Serve

Bake the pie in the preheated oven at 350°F (175°C) for 10-15 minutes or until meringue is golden. Allow to cool completely before serving. For the chantilly cream, whip heavy cream, powdered sugar, and vanilla until soft peaks form. Serve slices of pie with a dollop of chantilly cream.