Using a large serrated knife, slice the bread into 1-inch cubes. Spread half of the bread cubes in the bottom of the prepared baking dish. Sprinkle half of the blueberries on top. Top with the remaining bread cubes and finish with the rest of the blueberries, distributing evenly.

In a large bowl, add the lemon zest and brown sugar. Using your fingertips, rub the lemon zest into the sugar until well combined and fragrant.

Add the eggs, milk, melted butter, vanilla, and salt to the bowl. Whisk until well combined.

Slowly pour the egg mixture evenly over the bread and blueberries. Cover with foil and refrigerate for at least 4 hours or overnight (up to 12 hours).

When you’re ready to bake, preheat the oven to 350°F. Remove the pan from the refrigerator and allow it to sit at room temperature while the oven preheats.

Bake covered for 45 minutes. Remove the foil and continue to bake uncovered for another 10-15 minutes or until the french toast is evenly puffed and the custard in the center is cooked through.

Serve with maple syrup or powdered sugar.