Preheat oven to 350 degrees F.
In a medium-sized bowl, mix together crushed crackers, melted butter, granulated sugar, the egg white, and salt until fully combined.
Press cracker mixture into a 9-inch pie dish to form an even crust, then place crust in the fridge for 25 minutes.
After crust has chilled, bake for 18-20 minutes or until crust is beginning to turn golden in color. Allow crust to cool while you prepare filling.
In a large bowl, whisk together condensed milk and the egg yolks until well combined. Add lime and lemon juice and whisk until smooth.
Pour filling into the crust and bake for 15 minutes or until the center of the pie has only a slight jiggle.
Allow 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.