Set the oven temperature to 350°F (around 177°C). Line a 9-inch square baking pan with parchment paper, leaving an overhang on the sides.
Crush graham crackers into fine crumbs. Combine crumbs and sugar in a medium bowl.
Add melted butter and mix until combined. Press the mixture firmly into the prepared pan. Pre-bake for 10 minutes.
Beat cream cheese until smooth. Beat in egg yolks.
Add lime zest, sweetened condensed milk, and key lime juice. Beat until combined. Pour over the cooled crust.
Bake it for 18-20 minutes or until edges are set and the center is slightly jiggly.
Cool at room temperature for 30 minutes, then refrigerate for at least 2.5-3 hours.
Lift from the pan using parchment paper and cut into squares. Garnish as desired.