1. Spray a 9- by13-inch baking dish with nonstick spray. In a medium saucepan, over low heat, place the butter, brown sugar, corn syrup, zest and limeade and cook until butter and sugar have melted, 3-5 minutes. Pour into the baking dish.

2. In a small bowl, mix the eggs, milk and vanilla and blend well. Arrange the bread slices in one layer over the syrup mixture and pour the egg mixture over the bread. Cover and refrigerate overnight.

3. 30 minutes before baking, remove the French toast from the refrigerator and allow to return to room temperature. Preheat the oven to 350º and bake, uncovered, for 30 minutes, until golden brown. Serve immediately.