Place a 9 or 10 inch cast iron skillet in the oven and preheat to 425 °F.
In a blender, mix eggs on high speed for a few seconds until combined and bubbly.
Add flour, milk, vanilla extract, cinnamon and salt. Mix on medium-high speed until the ingredients are well combined, 5-10 seconds.
Remove the pan from the oven. Add the butter and swirl to coat the bottom of the pan. Pour in the batter and return to the oven.
Bake for 13-15 minutes until the Dutch baby is golden brown on top and has puffed up the sides of the pan. Turn the oven off and let it rest for an additional 5 minutes.
Remove from the oven and top with orange slices. Drizzle with orange liqueur (optional).
Place powdered sugar in a sifter (or use a small metal strainer) and dust the entire pancake with sugar. You can also dust with a little more ground cinnamon for a nice contrast with the powdered sugar.
To serve, cut in wedges and place on plates. Add more powdered sugar or ground cinnamon on the pancake and plate if desired.