Preheat your oven to 425°F (220°C).

In a mixing bowl, whisk together the eggs until frothy, about 1-2 minutes. Then, pour in the milk, add the flour, vanilla extract, and salt. Mix until smooth.

In a skillet over medium heat, melt the butter. Add sliced apples, brown sugar, and ground cinnamon. Sauté for 5-7 minutes until apples are tender.

Pour the prepared batter over the sautéed apples. Transfer to the oven and bake for approximately 20 minutes until puffed and golden brown.

Remove from oven, let cool for a minute, then slice and serve warm with powdered sugar or maple syrup.