Generously grease bottom and sides of a 9 x 13 baking dish with the melted butter.
In a large bowl, combine bread cubes and raisins. Toss to evenly disperse.
In another bowl, whisk eggs until well-blended. Add milk, brown sugar, vanilla, salt, cinnamon, and nutmeg. Stir until blended.
Add liquid mixture to bread mixture. Gently stir to fully coat and moisten bread cubes.
Transfer mixture to the prepared baking dish, cover with foil and let stand for about 30 minutes.
Bake in a 350 F oven for about 30 minutes or until pudding is mostly set and liquid is absorbed.
Remove foil and continue to bake for another 10 to 15 or until top is golden and a toothpick inserted in the center comes out clean. Remove from oven.
In a saucepan over medium heat, melt butter. Add sugar and stir until dissolved. Add heavy cream and orange juice, stirring constantly. Cook for about 2 to 3 minutes or until sauce is slightly thickened but still pourable. The sauce will continue to thicken as it cools.
Drizzle caramel sauce over bread pudding and cut into serving portions. Serve warm.