1. Beat the flour, milk, eggs, sugar, vanilla, and salt in a bowl or food processor until it is liquidy. (If you have time, allow to rest for 20 minutes.)
2. Place a 9 to 10-inch oven safe skillet on the middle rack of the oven and remove any racks above it. Heat the oven to 425°F.
3. When you are ready to make the Dutch baby, remove the skillet from the oven using oven mitts and place it on top of the stove. Add the butter and swirl the pan to melt the butter and coat the bottom and sides of the pan.
4. Pour the batter on top of the butter. Tilt the pan if needed so that the batter runs evenly to all sides. Place the pan back in the oven.
5. Bake until the Dutch baby is puffed, lightly browned across the top, 15 to 20 minutes.
6. Serve warm, either transferred to a plate or directly from the pan! Dust with powdered sugar and top with fresh berries!