Whisk together the eggs, granulated sugar, a pinch of salt, fresh lime juice, and lime zest in a medium saucepan until smooth.

Place the saucepan over low heat, stirring continuously for about 4-5 minutes until the mixture thickens.

Lower the heat and add the diced butter, stirring gently until it melts completely.

Strain the mixture through a fine mesh strainer into a clean jar or container to achieve a silky finish.