Preheat your oven to 325°F (160°C). In a large mixing bowl, combine the sweetened coconut, egg white, vanilla, and salt. Mix well until the coconut is evenly coated.
Press the coconut mixture firmly into the bottom and up the sides of a 9-inch pie dish. Make sure it is compact and even. Bake for 10-12 minutes, or until the edges are golden brown. Remove from the oven and let it cool.
In another mixing bowl, whisk together the sweetened condensed milk, egg yolks, lime zest, and lime juice until smooth and well combined.
Once the crust has cooled, pour the key lime filling into the coconut macaroon crust, spreading it evenly.
Bake the pie in the preheated oven for an additional 15-20 minutes, or until the filling is set but still slightly jiggly in the center.
Let the pie cool at room temperature, then refrigerate for at least 2 hours before serving to allow it to fully set. Serve chilled, garnished with additional lime zest or whipped cream if desired.