Cake: Preheat oven to 180 degrees C. Lightly grease a ring tin, dust with flour and shake out excess. Place on a baking tray lined with aluminium foil.
Cream together butter and oil in a large mixing bowl until fluffy, about 1 minute. Slowly pour in 1 cup of sugar and continue to beat until fluffy, about 2 to 3 minutes.
Beat in eggs one at a time, beating for about 10 seconds per egg. Stir in cake mix and blend until smooth. Add the sour cream, evaporated milk, flour and vanilla. Beat together for 2 to 3 minutes until smooth.
Bake in preheated oven until cake has a golden brown crust and springs back when pressed with a finger, about 60 to 70 minutes. Let cake sit in the pan for 20 minutes while proceeding to the next step.
Glaze Melt the butter in a small pan over medium heat. Stir in brown sugar and white sugar then bring to a gentle simmer and stir in the rum. Cook until the sugars have dissolved, then remove from heat.
To Serve: Unmould cake onto a serving dish. Gently poke holes into the cake with a fork or cake tester. Pour glaze evenly over cake. Top with toasted coconut.