In the top of a double boiler, beat eggs and yolks. Stir in 1/2 cup sugar, lime juice and peel. Cook over simmering water while gradually whisking in butter. Cook and stir until mixture is thickened and reaches 160°. Strain; refrigerate until completely cool.
In a small bowl, beat cream and vanilla until stiff peaks form; gradually beat in remaining sugar. Gently fold into lime mixture.
Split cake horizontally into three layers. Place bottom layer on a serving plate. Spread with 2/3 cup lime mixture. Repeat. Place top layer on cake. Frost top and sides with remaining lime mixture. Sprinkle with coconut. Refrigerate for at least 30 minutes before slicing.
How to satiate a sweet tooth? A great cake recipe can always do the trick. I found this one on Taste of Home and it is pretty good.