Recipe transcribed from an America's Test Kitchen video on YouTube:

Pancake:
Dry Ingredients – put in large bowl
1 ¾ cup all purpose flour
3 tbsp sugar (use less)
1 tbsp lemon zest
½ tsp salt
1/8 tsp nutmeg

Wet Ingredients:
1 ½ cups milk
6 large eggs
1 ½ tsp vanilla
Whisk wet ingredients till well combined.
Add 2/3 of wet mix to dry ingredients in large bowl; whisk to combine. Add remaining 1/3 of liquid and mix well.

To prepare batter for baking in oven proof skillet: (I used cast iron.)
Melt 3 tbsp butter and brush sides of oven proof skillet so pancake can be removed easily.
Pour batter into skillet and place in COLD oven, MAKING SURE TO MOVE THE OVEN SHELF ONE LEVEL LOWER THAN CENTER TO KEEP RISING PANCAKE FROM HITTING THE BROILER ELEMENT! Set temperature to 375°.

Topping Ingredients: (Prepare while pancake is in oven)
Melt 2 tbsp of butter on medium low heat in a 10”-ish skillet
Add 1 ½ pounds peeled apple cut into approx.. ½ inch chunks (I used Gala apples)
1/3 cup water
¼ cup brown sugar – (3 tbsp would have been fine)
¼ tsp cinnamon
Mix ingredients well to coat apples. Bring to a simmer (raise heat a bit) and cook COVERED for 5 minutes.
Remove cover and cook 5 minutes more to thicken liquid.

I was lucky and had both the pancake and topping get finished within mere seconds of each other. Make sure you have the topping finished when the pancake comes out of the oven.

Cut into wedges for serving. We each had ¼ of the pancake this morning and I couldn’t finish mine. A quarter of a pancake is a generous serving. Next time I will halve the ingredients and use a smaller skillet. While I’m refrigerating the leftovers I’m sure they won’t have as nice a texture when I reheat them.