Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking dish.
Cube the bread and place it in the prepared baking dish.
Prepare the custard: In a mixing bowl, whisk the eggs, milk, heavy cream, sugar, vanilla, cinnamon, nutmeg, and salt until smooth.
Pour the custard over the bread cubes. Gently press the bread down to soak up the mixture. Let it sit for 10-15 minutes.
Bake for 45-50 minutes, until the top is golden brown and a knife inserted comes out clean.
Make the sauce: In a saucepan, melt butter over medium heat. Stir in sugar, cream, vanilla, and salt. Bring to a simmer and cook for about 5 minutes.
Serve the bread pudding warm, drizzled with the sauce.