In a large bowl, beat the softened cream cheese until completely smooth and free of lumps.
8 ounces block-style cream cheese
Add the egg yolks and mix until fully incorporated. Pour in the sweetened condensed milk and beat until smooth.
6 large egg yolks, 28 ounces sweetened condensed milk
Add the key lime juice and lime zest. Mix until fully combined. The mixture will thicken slightly. Pour the filling over the warm crust and spread evenly.
1 cup key lime juice, 1 heaping tablespoon lime zest
Bake for 20–25 minutes, just until the center is set with a slight jiggle in the middle. Do not allow the top to brown.
Cool at room temperature for 30–45 minutes, then refrigerate for at least 4 hours or until fully chilled and firm.