Heat 1 tablespoon butter over medium heat in a 10 inch oven-safe skillet ( I used a cast iron skillet).
When the butter is melted, add the apples, 1 tablespoon light brown sugar and cinnamon. Stir to combine. Cook until apples start to soften, about 4 to 5 minutes.
While apples are cooking, melt the remaining tablespoon butter in the microwave. Pour it into a blender along with the eggs, milk, flour, vanilla, salt and remaining 1 tablespoon of sugar. Blend until smooth.
Pour the batter over the apples in the skillet and transfer the skillet to the oven.
Bake 20 to 25 minutes until puffed up and golden brown. Dust with powdered sugar and serve with maple syrup, if desired.
Serve immediately, as it will start to fall within minutes of being taken out of the oven.