Light Lemon Curd Buttercream

Have ready a fine-mesh strainer suspended over a medium bowl.

In the top of a double boiler set over barely simmering water (do not let the bottom of the container touch the water), whisk the egg yolks and whites with the sugar until well blended. Whisk in the lemon juice and salt. Cook over medium-low heat, stirring constantly with a silicone spatula (be sure to scrape down the sides o