Lemon curd

Put butter, sugar, juice, and zest into a glass bowl set over a saucepan of simmering water or you could use a double boiler. That is what I used.
Let butter melt, then gradually whisk in the beaten eggs.
Cook, stirring constantly, until it thickens. If you don't continually stir, trust me, there are clumps and it is not as smooth as it should be.
Once it thickens, remove the bowl or top pot from the water and let it cool.
Transfer the curd into a clean jar and bring it to room temperate.
Once at room temperature, you are able to refrigerate it up to a couple of weeks if it lasts that long.