In a large bowl, whisk together the eggs, sugar, cream, milk, vanilla extract, orange zest, and salt until smooth.
Preheat oven to 350˚F. Arrange the bread slices in a single layer in a deeply rimmed baking sheet or tray. Pour the custard mixture over the slices and allow to soak for 30 minutes, flipping the bread over at the 15 minute mark.
In a small bowl whisk together the melted butter and brown sugar. Line a large baking sheet with parchment.
Remove each slice of bread from the tray of custard, allow the excess to drip off, and place 1 inch apart on the parchment-lined baking sheet.
Brush each side of the bread slices with the brown sugar mixture. Bake in the preheated oven until the tops are golden and bubbly, about 20 minutes total and flipping the slices halfway through.
Serve the Creme Brulee French Toast warm with powdered sugar, maple syrup, whipped cream, and other desired toppings.