Preheat the oven to 350°F.
Prepare a 9 x 13 dish by spraying with nonstick spray.
Spread the cubed bread evenly in the bottom of the baking dish.
In a large mixing bowl, whisk together the eggs, milk, both sugars, vanilla extract, cinnamon, and nutmeg. Mix until all ingredients are well incorporated.
Pour the egg mixture over the bread cubes. Allow this to sit for about 10 minutes.
After the bread mixture has set for 10 minutes, drizzle the 4 tablespoons of melted butter on top of the soaked bread cubes.
Place the baking dish in the oven and bake for 45 minutes.
While the bread pudding is baking, in a medium sized saucepan, combine the light brown sugar, heavy cream, and butter to make your caramel sauce. Heat this mixture over medium heat.
Whisking intermittently, cook the caramel mixture for 5 to 6 minutes.
Remove the caramel sauce from the heat and whisk in the ½ teaspoon of vanilla extract.
Pour the caramel sauce over the bread pudding, immediately after removing the pudding from the oven. Serve while warm.