1. Grease a 10-cup microwave-safe ring mold with softened butter and coat with nuts and brown sugar. Set aside.
2. Combine sugar, orange juice, and egg in a 1 1/2-quart mixing bowl. Stir in baking mix to blend. Add walnuts and marmalade and stir only until all ingredients mixed. Pour batter into prepared mold.
Do not cover.
3. Set microwave oven at Time Cook (power level 5) for 6 minutes, and then Time Cook (power level 10) for 2 minutes. Rotate dish 1/2 turn after 5 minutes' cooking time. If necessary, microwave at Time Cook (power level 10) an additional 1 to 5 minutes, to complete baking. Let stand 5 minutes before inverting onto serving plate.