I found this recipe several years ago in a magazine and it has become a family favorite:
Chocolate Orange Cake
1 box chocolate cake mix
1 small box vanilla instant pudding
¾ cup orange juice
¾ cup oil
2 tablespoons grated orange rind
Mix ingredients and pour into Bundt pan. Bake at 350 degrees for 45 to 50 minutes until done.
Remove from pan and allow to cool.
Use one can of chocolate frosting and place in microwave at 15 second intervals until the frosting melts into a smooth, but not runny glaze. Spoon over cake and decorate with mandarin oranges (fresh or canned).