Place zest, lemon juice, yolks, honey and butter in the top of a double boiler.
Place over gently boiling water; the upper pan should not touch the water.
Cook, whisking often, until the curd thickens, about 15 minutes.
The curd will thicken more as it cools.
Transfer to a clean container.
Cover the surface with plastic wrap, so it touches the hot curd, to prevent a skin from forming.
Refrigerate.
