Cut unpeeled orange into 8 pieces. Remove core end parts and place in a blender or food processor. Add dates and orange juice, and blend until liquified. Add butter and egg, and blend until smooth (about 2 minutes).

In a large bowl, combine all remaining ingredients. Add orange mixture and stir lightly, just until ingredients are moistened.

Fold into a greased 9-inch square cake pan. Bake at 350°F for 44 to 50 minutes. Cake is done when it springs back when lightly touched.

Cake remains in the pan.

To make topping, melt butter in a small saucepan. Blend in remaining topping ingredients, and spread eveningly over the warm cake. Place oven rack 8 inches from broiler element. Broil cake for 2 to 3 minutes or until topping is bubbling and lightly browned. 

NOTE: The topping burns easily so do not leave unattended while broiling.