Pour key lime curd into a jar or glass bowl. Press a piece of plastic wrap directly against the curd so it is airtight and doesn't create a film on the top. Cool to room temperature and then place in the refrigerator. Again, the curd will thicken up even more after it is completely cooled.
Place lime zest, juice, egg yolks, maple sugar, ghee and vanilla extract in a medium heavy-bottomed saucepan and stir until combined. Turn on heat to medium-low heat and use a whisk to whisk constantly until the mixture melts and the begins to thickens, about 10-12 minutes. Yes, you need to whisk the entire time. The key lime curd will continue to thicken as it cools.
I eat paleo. If you did not notice from the blog name, well, that’s understandable. It’s not Pale Omg, like the skin color. I’m usually pretty tan. It’s actually pronounced pay-lee-o.m.g. There ya go, you did it! I just love food.