Orange Walnut Rum Cake with Grand Marnier Icing

1 cup butter or margarine
2 1/2 cups sifted all-purpose flour
1 cup granulated sugar
Grated rind of 2 oranges
Grated rind of 1 lemon
2 teaspoons baking powder
1 teaspoon baking soda
1/2 teaspoon salt
2 eggs
1 cup finely chopped walnuts
1 cup buttermilk or plain yogurt

Heat oven to 350 degrees F. Grease a 9- or 10-inch 2-quart tube pan.

Cream butter; gradually add sugar and beat until light. Add fruit rinds; add eggs one at a time, beating thoroughly after each. Add sifted dry ingredients alternately with buttermilk, beating after each addition until smooth. Fold in nuts. Pour into prepared tube pan. Bake for 1 hour.

Pouring Liquid:
1 cup granulated sugar
1 cup orange juice
3 tablespoons lemon juice
4 tablespoons rum

Strain fruit juices into saucepan. Add sugar and rum; bring to boil. Pour slowly over hot cake in pan. If all liquid is not absorbed, pour remainder on later.

Grand Marnier Icing:
1/3 cup butter or margarine
2 cups confectioners' sugar
1 tablespoon grated orange rind
Grand Marnier

Bring butter to room temperature. Mix all ingredients, adding enough Grand Marnier to make a good spreading consistency. Spread on cooled cake.