Move oven rack to the middle position and preheat to 325 degrees F. Line an 8x8-inch square baking pan with 2 sheets of foil so that there is a foil overhang on all sides. Spray the foil with nonstick cooking spray, and set the pan aside.
MAKE THE CRUST:
In a small bowl add the graham cracker crumbs, brown sugar, and melted butter. Stir until the mixture is combined and the graham cracker crumbs are evenly moistened with the butter.
Pour the crumbs into the prepared pan and use your hands to press the crumbs firmly into an even layer. Bake the crust until it’s deep golden brown in color, about 16-20 minutes. DO NOT TURN OFF THE OVEN! Move crust to a wire rack while you prepare the filling.
MAKE THE FILLING:
In a medium bowl, whisk together the cream cheese, lime zest, and salt until the creamy and smooth. Pour in the sweetened condensed milk, egg yolk, and lime juice and whisk until combined and smooth.
BAKE, CHILL, AND SLICE:
Pour the filling over the slightly cooled crust and smooth into an even layer by carefully tilting the pan.
Bake for 15-20 minutes or until the filling is set. Move the Key Lime Bars to a wire rack to cool to room temperature, this will take about 1 hour. Then, cover the bars with foil and chill for at least 2 hours. When you’re ready to serve the bars, use the foil overhang to lift the bars from the pan and slice into 9 squares.
Serve with any of the following garnishes: powdered sugar, whipped cream, lime wedges, fresh raspberries, and/or toasted coconut (all optional).
The nutritional value that is posted is based on 1 Key Lime Bar without any of the garnishes.