How to Make It
Pour water to a depth of 1 inch into bottom of a double boiler; bring to a boil. Reduce heat, and simmer. Whisk eggs and egg yolks in top of double boiler away from heat; whisk in sugar, rind, and lemon juice. Place over simmering water. Cook, whisking constantly, until curd thickens, about 6 minutes.
Remove top of double boiler from simmering water, and add butter, whisking until melted. Pour mixture through a wire-mesh strainer into a bowl, discarding solids. Press plastic wrap directly onto surface of lemon curd to prevent a skin from forming, and chill at least 8 hours.