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.
1/2 cup fresh grapefruit juice, 1/4 cup honey, 2 large eggs, 2 large 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.
5 tablespoons salted butter
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.