Step 1

In a medium (2 qt) saucepan, combine eggs, sugar, zest, and a pinch of salt. Whisk vigorously until well combined, frothy, and lightened in color.

Step 2

Whisk in lemon juice until blended.

Step 3

Add butter pieces and set the pot over low heat, whisking constantly until the butter is melted and the mixture is thickened (7-9 minutes). The lemon curd will thicken around 160-170˚F. Once you see it start bubbling, let it gently simmer for a few seconds then remove it from the heat at around 175-180˚F on a thermometer. When it's ready, it should coat the back of a spoon without running when you pull your finger across the spoon.

Step 4

Strain the mixture through a fine sieve (if you stir in the sieve with the whisk, it will push the mixture through the sieve faster). Discard the solids left in the sieve.

Step 5

Stir in vanilla extract. Let the mixture cool to room temperature then store covered in the refrigerator to fully set. Keeps well in the refrigerator for up to a week.