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 constantly, until the mixture is thickened. It should be thick enough to coat the back of a spoon.
Remove from heat and whisk in butter, a few pieces at a time, whisking until all the butter is incorporated.
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.