Preheat oven to 425 degrees.
Place butter in a 10 inch cast iron skillet and place in oven to melt.
Beat eggs with a hand-held electric mixer for 3-4 minutes until pale and frothy.
Beat in flour, milk, cinnamon and vanilla until smooth. (about 1 minute)
Pour batter into skillet and bake for 18-22 minutes until golden and puffy.
While Dutch baby is baking, make caramelized peaches.
In a medium bowl whisk together sugar, salt and cinnamon.
Add sliced peaches and toss to coat.
Heat a skillet over medium-high heat.
Add peaches and cook, stirring occasionally for 5-7 minutes until soft, bubbly and the sugar caramelizes.
Add butter and continue to cook for one minute.
Pour over the Dutch baby and serve immediately. Dust with confectioners sugar if desired.