Preheat oven to 350 degrees F.

Make the Filling: Whisk the lime zest and egg yolks in a medium bowl for 2 minutes. Whisk in the sweetened condensed milk, then the lime juice. Set aside at room temperature to thicken while you prepare the crust.

Make the Crust: Stir together the graham cracker crumbs, brown sugar, and salt. Drizzle the melted butter over the mixture and toss to combine. Press into a 9-inch pie plate and bake for 10 minutes. Cool.

Pour the lime filling into the cooled crust and bake until the center is set yet wiggly, about 15-17 minutes. Cool to room temperature, then refrigerate for at least 3 hours or overnight.

Make the Whipped Cream: Whip the chilled cream until soft peaks form, add the powdered sugar, and vanilla, then whip to stiff peaks. Pipe or spread over the chilled pie.

Garnish with lime slices and serve. Cover leftovers with plastic wrap and refrigerate for up to 3 days.