Apple Dutch Baby

Dutch Baby Batter
2 Preheat the oven to 425 F.
3 In a medium bowl, add in the sugar and lemon zest. Rub the zest into the sugar with your fingers. Then add in the eggs, vanilla, and salt and whisk until smooth.
4 Pour in the milk and whisk again.
5 Lastly whisk in the flour. Continue whisking until completely smooth.
6 Cover the bowl and let the batter rest at room temperature for 10 minutes. While it rests, start cooking the apples.
Cook the Apples
8 Add 1 tablespoon of butter into the cast iron pan and place over medium heat until melted.
9 Slice the apple (no need to peel it) into 1/4" to 1/2" thick slices, don't cut them too thin or they'll kinda disappear. Add the sliced apples into the melted butter and cook until soft - stirring frequently to keep them from browning about 5-10 minutes.
10 Add in another tablespoon of butter into the center of the pan, it should melt immediately. Don't turn off the heat.
11 Pour the rested batter through a fine mesh sieve and push through any clumps of flour. Then quickly but gently pour the batter over the apples.
Bake
13 Quickly place the pan into the hot oven and bake for 20 minutes.
14 Once baked, it should be puffy and golden brown, remove the pan from the oven and place on a heat safe surface.
15 Squeeze the juice of half a lemon over the top and then dust it with powdered sugar.