Fill a saucepan with 2 inches of water and set to simmer.
In a stainless steel or heatproof bowl, whisk together grapefruit juice, honey, eggs, and egg yolks.
Set the bowl over the simmering water and cook, whisking to melt the honey and blend the ingredients.
Whisk in butter, a few pieces at a time, whisking until all the butter is incorporated. It should be thick enough to coat the back of a spoon.
If your curd looks lumpy, press it through a sieve. Pour into jars and store in the refrigerator for at least two hours before serving. The curd will keep in the refrigerator for about a week, or 1 month in the freezer.