PREPARE THE CRUST

1. Preheat the oven to 350°F. Line a baking sheet with parchment paper and place a 9- or 10-inch tart pan with a removable bottom on top. Set aside.
2. Break the graham crackers into pieces and pulse in a food processor until fine crumbs form.
3. Transfer the graham cracker crumbs to a mixing bowl and stir in the sugar and salt.
4. Add 4 tablespoons (56g) of melted butter and stir until the crumbs are evenly moistened and hold together when pressed between your fingers. If the mixture seems dry or crumbly, add an additional tablespoon of butter.
5. Transfer the crumb mixture to the tart pan and spread it evenly across the bottom and up the sides. Use the flat bottom of a measuring cup or glass to firmly press the crust into place.
6. Bake for 10–12 minutes, or until lightly golden and fragrant.
7. Transfer the pan to a wire rack and allow the crust to cool slightly.

MAKE THE FILLING

1. Reduce the oven temperature to 325°F.
2. In a large mixing bowl, whisk together the egg yolks and lime zest for about 1 minute, or until slightly thickened.
3. Add the sweetened condensed milk and salt and whisk until smooth.
4. Pour in half of the key lime juice and whisk gently to combine. Add the remaining juice and continue whisking until the filling is smooth and creamy. The mixture may briefly look slightly separated at first but will become smooth again as you continue whisking.
5. Let the filling rest for 5–10 minutes to thicken slightly.
6. Pour the filling into the cooled crust and spread into an even layer.
7. Bake for 15–22 minutes, or until the edges appear set and the center still has a slight wobble.
8. Transfer the tart to a wire rack and cool to room temperature, then refrigerate uncovered for at least hours.

MAKE THE WHIPPED CREAM

1. Add the heavy cream, powdered sugar, and vanilla extract to a large mixing bowl or the bowl of a stand mixer fitted with the whisk attachment.
2. Beat on medium-high speed until medium peaks form.

GARNISH AND SERVE

1. Remove the tart from the refrigerator and let sit at room temperature for about 5 minutes before removing the pan.
2. To release the tart, place the pan on top of an upside-down bowl or large can. Gently press downward on the outer ring while lifting the bottom upward to release the sides.
3. Spread or pipe the whipped cream on top of the tart and garnish with extra lime zest or lime slices if desired.