In a small saucepan, whisk together the egg yolks and sugar until a pale yellow color.

Whisk in the lemon juice, zest and salt until well combine. Bring to the stove and cook over medium heat whisking well until it thickens. It will take about 10-15 minutes. You know it is done when it coats the back of a wooden spoon and doesn't run.

Lastly, whisk in the butter and pour into a jar, cover and set in fridge. Once cooled, enjoy it! It will last in the fridge for a week.