01 - Preheat oven to 350°F (180°C). Grease a 9 x 13 inch baking dish with softened butter.
02 - Distribute the panettone cubes evenly in the buttered baking dish.
03 - In a large mixing bowl, whisk together eggs, granulated sugar, whole milk, heavy cream, vanilla extract, orange zest, and ground cinnamon until fully blended.
04 - Pour the custard mixture evenly over the panettone cubes. Press down gently so the bread absorbs the liquid.
05 - Dot the surface with remaining softened butter. Let the assembled pudding stand for 10 minutes to allow thorough soaking.
06 - Bake for 35 to 40 minutes, or until the custard is set and the top is golden brown.
07 - Remove from the oven and let the bread pudding cool for 10 minutes. Dust with powdered sugar before serving.