In a large bowl, whisk together 4 eggs, 1 cup of all-purpose flour, 1 tablespoon of granulated sugar, 1 teaspoon of baking powder, and a pinch of salt. Gradually mix in 1 cup of milk until the batter is smooth. Add 1 teaspoon of vanilla extract, 2 tablespoons of melted unsalted butter, and a sprinkle of ground nutmeg; stir until just combined. Let the batter rest for 30 minutes.

Preheat your oven to 425°F (220°C).

Melt 1/4 cup of unsalted butter in a 10-inch oven-proof skillet over medium heat and coat the sides.

Mix together 2 tablespoons of granulated sugar with 1 teaspoon of ground cinnamon and a pinch of nutmeg. Sprinkle over the melted butter.

Slice 2 tart apples thinly and layer them in the skillet over the sugar mixture. Cook for about 2-3 minutes until slightly softened.

Gently pour the prepared batter over the caramelized apple layer without stirring. Place the skillet in the oven to bake for about 15 minutes.

After 15 minutes, reduce the oven temperature to 375°F (190°C) and continue baking for another 10 minutes.

Remove from the oven, let it cool for a minute, and cut into wedges to serve warm. Optionally, pair with powdered sugar or yogurt.