Caramelized Apple and Cinnamon Skillet Cake

Ingredients

2 large apples, peeled and sliced.

1/2 cup sugar.

1 teaspoon cinnamon.

1/2 cup butter, melted.

1 cup all-purpose flour.

1 teaspoon baking powder.

1/2 cup milk.

1 egg.

1 teaspoon vanilla extract.