Position a rack in the middle of the oven and preheat to 325 degrees Fahrenheit. Lightly butter a 2½-quart ovenproof serving dish about 4 inches deep.
In a large bowl, whisk the eggs. Whisk in the sugar. Whisk in half-and-half and cream. Whisk in the orange juice, vanilla, orange zest, cinnamon and nutmeg.
Scatter half the strawberries and half the blackberries over the bread cubes. Scatter the remaining bread cubes over the berries. Scatter the remaining berries over the bread cubes. Pour the egg mixture over the bread cubes and berries. Lay a sheet of plastic wrap directly onto the surface of the pudding.
Weight it with 2 or 3 small ramekins or saucers so that the bread is completely immersed in the egg mixture. Let stand for 10 minutes.
Remove the weights and the plastic wrap. Set the pudding in the oven and bake until the top is lightly browned and the custard is set but not firm when the dish is jiggled. About 50 to 60 minutes.
Let the pudding rest in the dish on a rack for at least 10 minutes. Sift confectioners' sugar through a sieve onto the bread pudding and serve hot or warm, accompanied by the berry sauce (recipe below).