In a medium to large sauce pot, zest grapefruits then squeeze in juice of both grapefruits or add grapefruit juice.

Add fresh cranberries or cranberry juice.

Add lemon juice and sugar and stir.

Bring mixture to a boil and simmer for 3-4 minutes or until cranberries pop open and then boil for another minute after they pop open, if using juice and not fresh cranberries then bring to a boil and cook until sugar dissolves.

Remove juice mixture from heat and pour through a fine mesh strainer to remove the cranberries and other bits of grapefruit, after straining place mixture back into pot.

Set aside while you prepare the egg yolks.

In another bowl, add egg yolks and whisk together.

Spoon in about 1 tablespoon of the hot mixture and whisk into the egg yolks, followed by another tablespoon and another until you've added about 1/2 cup into the eggs.

This is called tempering our eggs and helps not get chunky fruit curd.

Once all the hot mixture is mixed into the eggs, add egg and juice mixture into the rest of the juice mixture and turn heat on medium high, whisk continuously while you cook the mixture for 7-8 minutes.

You do not want the sauce to scorch on the bottom of the pan so you need to be attentive to both heat and whisking to avoid this.

Once mixture thickens and can coat the back of a spoon with a semi-thickened consistency then it is good and can be removed from heat.

Take cold butter and add in chunks to mixture while whisking and stir until butter dissolves.

Allow curd to cool completely for thickness of curd to fully develop.

This will store in the refrigerator for about 1 week.