In the bowl of food processor, mix the butter and sugar for about 2 minutes.
Slowly add the eggs and yolks and mix for for 1 minute.
Add the Key Lime Juice and mix to combine. The mixture will look curdled, but it will smooth out as it cooks.
Pour mixture into three one-cup Mason jars and place the lids, turning until the lid just catches.
Place 1.5 cups of water in the Pressure Cooker and place a trivet inside. Place Mason jars on top of trivet.
Lock on lid and close the Pressure Valve. Cook at High pressure for 10 minutes. When Beep is heard, allow a 10 minute Natural Pressure Release.
Remove jars from Pressure Cooker and carefully open. Add in the Key Lime Zest and stir into the curd. Place lids on Curd and tighten just until the lid catches.
Allow to cool for 20 minutes and then place in the refrigerator overnight. Curd will thicken as it cools.
Notes
Curd will keep in the refrigerator for a week or in the freezer for 2 months.One large container can be used in place of individual jars.