Preheat the oven to 350°F (175°C) and lightly spray a baking dish with nonstick cooking spray.

Whisk together the eggs, milk, sugar, lemon zest and juice, vanilla extract, and cinnamon in a large bowl until well combined.

Layer half the cubed bread in the baking dish, sprinkle half the blueberries on top, then pour half the custard mixture over them.

Repeat with the remaining bread, blueberries, and custard.

Cover the dish and refrigerate for at least an hour or overnight to soak.

Bake uncovered for 45-50 minutes until golden brown and the center is set.