Try this cake filling recipe by cooking guru James Beard.
3/4 cups Orange juice — strained
2 tbs Lemon juice
3/4 cups granulated sugar
1 tb Orange rind — finely grated
Mix the orange juice, lemon juice, sugar and orange rind together and drizzle the mixture over the three still warm cake layers. Be careful not to let it all soak into one spot. Then pile the layers on top of each other. The juice mixture will give the cake a lovely, fresh, fruity flavor and it is not rich like a chocolate or other candy flavored icing. Leave the cake to cool.