Cream butter and sugars until light and fluffy. Add eggs, egg yolk, and vanilla, beating until blended. Add orange extract, beating until blended. Gradually add rum and sour cream, beating until blended.
Sift together flour, baking soda, baking powder, and salt. Add alternately with whipping cream, beginning and ending with flour mixture. Beat batter until blended after each addition. Pour batter into a greased and floured 10-inch Bundt pan.
Bake at 350° for 55 to 60 minutes or until a long wooden pick inserted in center of cake comes out clean.
Cool in pan on a wire rack 15 minutes. Remove from pan and allow to cool completely on wire rack. Ice with Coconut Rum Icing.
Coconut Rum Icing Directions:.
Melt together butter and milk over low heat in small sauce pan. When melted stir in Rum and sugar. Whip with wire whisk until thick enough to pour over cake. If necessary add more sugar or hot water to adjust thickness of icing. Stir in flaked coconut.
Place cake on wire rack over cookie sheet (line with foil or wax paper to speed cleanup) and pour icing over cake. Use an offset spatula to smooth icing if necessary to cover cake. Sprinkle with a little flaked coconut for garnish.