Preheat the oven to 350°F (180°C). Coat a 13 x 9-inch (33 x 23 cm) baking dish with melted butter.
Arrange the bread slices to fit in a single layer in the dish; sprinkle cinnamon over the bread.
In a medium bowl, whisk the eggs, milk, syrup, butter, and vanilla just until blended. Pour mixture evenly over the bread, then flip each slice to soak up remaining egg mixture and ensure each piece of bread is evenly coated and saturated.
Bake, uncovered, until firm to the touch, about 30 minutes. Or, cover and refrigerate several hours or overnight before baking.
Serve with fruit, jam, maple syrup and/or whipped cream, as desired.