Melt butter in a small saucepan. Add sugar, orange juice and stir well. Add nuts. Bring to a boil, then reduce heat and cook for 5 minutes Remove from heat and set aside to cool to room temp slightly. Add rum and powdered sugar. Stir well. Poke holes all over cake with a skewer. Pour glaze over cake while still warm and top with remaining nuts. Allow cake to stand for at least an hour before slicing.