Place a 10-inch or 12-inch cast iron skillet on the center rack of your oven and preheat oven to 425°F (220°C). Heating the skillet is the secret to a towering puff!

In a blender, combine eggs, whole milk, flour, sugar, vanilla extract, nutmeg, and salt. Blend on high speed for 30 seconds until completely smooth and frothy. Let batter rest at room temperature for 10 minutes while skillet heats.

Carefully remove the hot skillet from the oven using heavy oven mitts and set it over medium-low heat on the stovetop.

Melt the 3 tablespoon of butter until foaming. Add sliced Honeycrisp apples, brown sugar, and cinnamon. Sauté for 3 to 4 minutes until apples begin to soften and sizzle in golden cinnamon caramel. Spread apples in an even layer across the skillet bottom.

Immediately pour the blender batter directly over the sizzling caramelized apples in the hot skillet.

Transfer skillet into the 425°F (220°C) oven and bake undisturbed for 18 to 20 minutes until edges puff dramatically tall above the pan rim and turn deep golden brown. Do not open the oven door during the first 15 minutes!

Remove from oven (it will naturally deflate slightly into a custardy center). Dust generously with powdered sugar, slice into warm wedges, and drizzle with warm maple syrup. Serve immediately!