Soak the zest in the lemon juice, then use the fine-mesh strainer to remove zest. (This is for flavor, we do not want the zest texture).

MEANWHILE, melt and cool the butter. Strain the butter through the fine-mesh sieve to decrease graininess, then wash the sieve right away so it's ready for the next step.

Prepare fine mesh sieve over a cold bowl so it is ready.

Separate eggs.

Whisk all ingredients together in a medium saucepan. Set to medium-low. Whisk constantly until thickened and will coat the back of a spoon (about 10-15 minutes). Higher temp will cause egginess.

Remove from heat and pour through a fine mesh sieve into a cold bowl.

Cover the hot curd with plastic wrap, tightly against the surface so it does not form a skin. Refrigerate until cold, then move to a sterilized jar with a lid. Store in the fridge, will keep for up to one week.