In a large sauté pan, melt the butter over med heat. Add the brown sugar, cinnamon and salt and whisk until the sugar has dissolved. Next, add the vanilla paste and the rum, whisking carefully as the mixture will begin to bubble. Now, stir in the nuts. Remove from heat and set aside.
Spray a 9"x13" casserole dish lightly with cooking spray. Arrange the banana slices in a single decorative layer. If you have excess slices, arrange them against the sides of the pan. Carefully, pour the sugar mixture over the bananas; making sure to cover them completely. Cover the bananas with the bread slices.
Prepare the custard by whisking together, in a large bowl, the eggs and yolk, half and half, cream, sugar, vanilla, spices, salt and orange zest. Whisk for at least 3 minutes to ensure the sugar has dissolved. Pour the mixture over the bread. Cover the pan with aluminum foil. Allow the bread to soak for 10 minutes.
Meanwhile, bring a pot of water to boil and preheat your oven to 350°F. Once the water has boiled, and your oven is heated, place the casserole dish in a larger pan and fill the outer pan halfway with boiling water. Carefully, place the pan into the oven centered on the rack. Bake for 1 hour.
After an hour, carefully remove the foil and allow the casserole to bake for an additional 10 minutes to brown the top. Remove from the oven and allow to cool, in the water bath, for 10-15 min. Take the casserole dish from the water bath and serve, or allow to cool for 10 minutes more and carefully invert onto a larger platter if you wish to display the topping.
Serve topped with powdered sugar and maple syrup, or with whipped cream and fresh berries. Enjoy!