- 6 cups confectioners' sugar
- 1 egg yolk
- 2 tablespoons lemon juice
- 3 tablespoons orange juice
- 1 lemon
- 2 large oranges
- 1/4 cup butter
- Beat the butter until it has the appearance of thick cream, stir in confectioners sugar, a little at a time, and continue working until mixture is very smooth. Beat in egg yolk and lemon juice. Stir in enough orange juice to make a spreadable frosting, then add grated rind of 1 lemon and 2 grated orange rinds. Spread on sides and top of cake.