In a small saucepan set over medium-low heat, add leftover cranberry sauce.
Stir in the orange zest, lemon zest, and maple syrup.
Season with a pinch of salt.
Stir together and heat until warmed through.
Remove the pan from the heat and set aside.
In a blender, combine the eggs, milk, flour, salt, and vanilla bean seeds. Blend until frothy, about 1 minute.
Add the butter to a 10-inch (25 cm) cast iron skillet and place in the oven to melt. Once the butter is melted and bubbling, carefully remove the pan from the oven, tilting to coat the pan evenly.
Dollop the cranberry sauce into the pan and pour the Dutch baby batter overtop; immediately return the skillet to the oven.
Bake until puffed and golden around the edges, 18 to 22 minutes.
Remove the Dutch baby from the oven and dust with Confectioners’ sugar.