Preheat the oven to 375 degrees F. Place a 10- to 12-inch cast iron skillet in the oven with 2 tablespoons of butter in it.
Add all the remaining ingredients to a blender. Puree until frothy. (Make sure the eggs and milk are room temperature. Cold dutch baby batter won't bubble and rise as well.
Open the oven and carefully swirl the melted butter around the pan. Pour the batter into the skillet. Bake for 20-30 minutes until puffed and golden.
Remove from the oven and use a flat metal spatula to move the Dutch baby to a cutting board. Cut into wedges and serve warm with fresh apple slices and vanilla yogurt.