Put egg yolks, zest, lemon juice, and honey into the top of a double boiler. You can make your own double boiler by simply placing the ingredients into a glass or metal bowl and setting that over a pan of gently simmering water. Just make sure the bowl does not touch the water.

Whisk the ingredients until the curd thickens, about 15 minutes.

Add in 1 tablespoon of the butter at a time until all pieces are incorporated.

Remove from the heat and store in a clean container. Some cooks prefer to strain their curd to give it a really silky smooth texture. Personally I don't mind the lemon zest adding a little texture, so I skip this step.

Refrigerate. If you want to prevent a skin from forming on top of the curd you can place plastic wrap on the surface. That doesn't bother me, so we usually just store it as is and enjoy!