In a medium-sized bowl, mix together the crushed crackers, melted butter, granulated sugar, egg white, and salt until fully combined.
Press the cracker mixture into a 9-inch pie dish to form an even crust. Place the crust in the fridge for 25 minutes.
After the crust has chilled, bake for 18-20 minutes, or until the crust begins to turn golden. Allow the crust to cool while you prepare the filling.
In a large bowl, whisk together the sweetened condensed milk and the egg yolks until well combined. Add the lime and lemon juice and whisk until smooth.
Pour the filling into the crust and bake for 15 minutes, or until the center of the pie has only a slight jiggle.
Allow the pie to cool to room temperature, then chill in the refrigerator for at least 2 hours before serving.
Before serving, top with whipped cream and lime zest, if desired.
