In a medium bowl, whisk sugar, eggs, egg yolks, and lemon zest.

In a medium saucepan, warm the lemon juice until steaming. Do not boil.

Temper the hot juice into the egg mixture, adding a small amount at a time and whisking well after each addition, until all of the juice has been incorporated.

Return mixture to saucepan and cook over medium heat. Bring to a low boil and continue cooking until thickened, about 4 minutes. While cooking, gently stir the curd continually with a wire whisk or rubber spatula.

Remove from heat. Whisk in the butter and the vanilla bean paste, and continue whisking until the butter has completely melted.

Transfer curd to a clean bowl.

Cover with clingfilm/plastic wrap, allowing the plastic to touch the top of the curd to prevent a tough skin from forming.

Refrigerate until ready to use.

Before serving, use a wire whisk to “knock back” the curd, whisking for 1-2 minutes or until smooth and creamy.

Store leftover curd in an airtight container in the refrigerator for up to three days.