Gather the ingredients.
In a medium bowl whisk the eggs, yolks, sugar, lemon zest and juice, and salt until well combined.
Transfer the mixture to a heat-proof glass container large enough to fit in the Instant Pot. Cover the container tightly with foil.
Pour 1 cup of water into the Instant Pot fitted with a trivet and carefully place the container onto the trivet.
Seal the Instant Pot lid. Pressure cook at high pressure for 3 minutes, then naturally release for 10 minutes.
Carefully remove the container from the Instant Pot. The egg mixture should be thick and set like a custard with small bubbles on top.
Add the butter, 1 tablespoon at a time, whisking between additions until melted well combined. As you whisk, the mixture should turn from clumpy to smooth and creamy.
Cover with a tight-fitting lid and let the mixture cool, about 30 minutes. Transfer to the refrigerator for at least four hours or up to overnight before serving.
