Combine graham cracker crumbs, sugar, and melted butter until evenly moistened. Press firmly into a 9-inch pie dish and bake at 350°F (175°C) for 8-10 minutes until golden.

Allow the crust to cool completely on a wire rack.

In a saucepan, whisk together sugar, cornstarch, flour, and salt with water over medium heat until thickened, about 5-7 minutes.

Temper egg yolks with some of the hot mixture, then return to pan and cook for another minute. Mix in butter, lemon zest, and lemon juice until smooth.

Pour the lemon filling into the cooled crust, chill in the refrigerator for 30 minutes.

Beat cream cheese with powdered sugar and vanilla until smooth. Fold in heavy cream and spread over lemon filling.

Cover with plastic wrap and refrigerate for at least 4 hours. Garnish with whipped cream and lemon slices before serving.