In a large bowl, toss together and thoroughly combine the bread, cranberries, rosemary, and lemon zest. Transfer the mixture to a greased 9" x 13" pan and set aside.
In the same bowl you used to mix the bread, whisk together the milk, heavy cream, eggs, sugar, vanilla, and salt. Pour over the bread. Cover and refrigerate for a minimum of 1 hour, or up to overnight.
When you're ready to bake, preheat the oven to 350°F. Remove the bread pudding from the refrigerator, uncover and give it a stir.
To make the topping, whisk together the sugar and nutmeg. Sprinkle generously over the top of the pudding.
Bake for 1 hour, uncovered, until set. Serve warm.
Refrigerate any leftovers, well wrapped, for several days.