Preheat your oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy removal.
In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Mix until well combined.
Press the mixture firmly into the bottom of the prepared baking pan to create an even crust layer. Bake for 8-10 minutes until golden. Remove from the oven and let cool slightly.
In a separate mixing bowl, whisk together the eggs, sweetened condensed milk, fresh key lime juice, lime zest, and vanilla extract until smooth and well blended.
Pour the filling over the cooled crust, spreading it evenly.
Bake for an additional 15-20 minutes, or until the filling is set and just slightly jiggles in the center.
Remove from the oven and let the bars cool to room temperature, then refrigerate for at least 2 hours (or up to overnight) until completely chilled.
Once set, use the parchment paper to lift the bars out of the pan. Cut into squares or rectangles.
Serve chilled, topped with a dollop of whipped cream and a slice of lime for garnish.
Notes
Chill the bars for a firmer texture before serving.