Creating Easy Skillet Upside Down Apple Pancake is straightforward if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).

2. Prepare the Skillet: In a 10-inch oven-safe skillet, melt the butter over medium heat.

3. Add Brown Sugar and Cinnamon: Stir in the brown sugar and cinnamon until well combined. Cook until the mixture is bubbling.

4. Arrange the Apples: Layer the sliced apples evenly over the bubbling mixture, making sure they are well distributed.

5. Prepare the Batter: In a mixing bowl, whisk together the flour, baking powder, and salt. In another bowl, combine the milk, egg, and vanilla extract.

6. Combine Mixtures: Slowly pour the wet ingredients into the dry ingredients, stirring until just blended. Avoid over-mixing.

7. Pour Batter: Carefully pour the batter over the apples in the skillet, ensuring even coverage.

8. Cook on Stovetop: Let the pancake cook on the stovetop for 5-7 minutes, until the edges start to set.

9. Transfer to Oven: Place the skillet in the preheated oven and bake for 15-20 minutes, or until the pancake is golden brown and a toothpick inserted into the center comes out clean.

10. Cool and Flip: Allow the pancake to cool slightly for a few minutes off the heat. Then, carefully invert it onto a serving plate.