Preheat the oven to 375 degrees F (190 degrees C).

Toss bread cubes, raisins, melted margarine, and cinnamon together in a large bowl until well mixed; transfer to a 2-quart baking dish.

Beat eggs in same bowl; stir in sugar, vanilla, and salt until sugar dissolved. Slowly whisk in hot milk; pour over bread cubes, sprinkle with nutmeg, and set aside to soak for 5 minutes.

Bake in the preheated oven until a knife inserted into the center comes out clean, 25 to 30 minutes.