Grease a 12-cup Bundt pan with the tablespoon of softened butter. Spread orange marmalade evenly around the bottom of the pan and sprinkle with nuts. In a small bowl, combine cinnamon and brown sugar and mix well.

Separate biscuits and cut each biscuit in half. Dip biscuit halves in melted butter, then into brown sugar mixture. Stand round edge of biscuits in Bundt pan, pressing them against each other. If there is butter and sugar remaining, combine and pour over biscuits.

Bake at 350° for 30 to 40 minutes. Remove from oven and cool upright for 5 minutes, then invert onto serving plate. Leave pan over cake for 10 minutes before serving. Remove pan and serve.