Beat the sugar, egg yolk and lemon juice in a saucepan over very low heat or in a water bath until the cream thickens - but does not boil. Add the grated lemon zest and mix in. Beat the egg white together with the salt until stiff and immediately fold into the egg yolk mixture.
Chop up the macaroons and place in a dessert bowl or serving mold as a base. Pour the cream on top and place in the refrigerator for at least 1 hour before you can eat it.
Tip: Serve garnished with whipped cream and lime zest before serving.