Gather the ingredients.
Place a large rimmed sheet pan in the center of the oven and preheat the oven to 400 F. After the oven reaches 400 F, allow the sheet pan to sit for an additional 5 minutes in the hot oven while you prepare the custard.
Break the eggs into a wide, shallow bowl or pie plate and beat them lightly with a fork or whisk. Whisk the milk, sugar, salt, and, if using, vanilla extract and cinnamon, into the beaten eggs. Set aside.
Place the bread slices, one at a time, into the bowl or plate with custard. Let the bread soak up the egg mixture for a few seconds and then carefully turn to coat the other side. Place soaked bread on a separate plate and continue until all bread is soaked.
Carefully remove the hot sheet pan from the oven and add the butter to the pan, spreading it around until it melts.
Add the soaked bread slices to the buttered pan, spacing evenly. Return the pan to the oven and reduce the temperature to 375 F. Cook until the bottoms of the bread are evenly burnished and golden brown, about 15 to 20 minutes.
Flip each piece of bread and return the pan to the oven to cook until the bread is browned on the other side, an additional 6 to 8 minutes. Serve immediately with toppings of your choice.