Preheat oven to 400°. Place butter in a 9-inch cast-iron skillet or a casserole. Place pan in oven to preheat and melt the butter. Watch it so the butter doesn’t burn while you make the batter—better yet, set a timer—and remove pan from oven when hot and butter is a bit bubbly.

Cut apple in quarters, core and slice into thin wedges. Toss with brown sugar and set aside.

Beat eggs well with a whisk. Mix flour in just enough to be smooth. Whisk in milk, salt and flavoring if using.

Pour batter into still-hot pan and place in hot oven. About 12 minutes into cooking, the sides of the pancake should be puffed up high. Remove pan, quickly strew the apples around the pancake, drizzle with the juice from the bowl and return to the oven. The puffy sides will fall a bit as you do this but that’s OK.

[Note: You can also make this pancake by slicing the apples a little thicker and putting them on top of the batter at the beginning—one step simpler and still good but it puffs differently. Adding apples halfway through cooking allows the whole cake to puff. Try both ways and see if you have a preference.]

Bake for a total of 25–30 minutes, until nicely browned and apples are cooked. Cut in wedges and serve hot with maple syrup, cider syrup or cinnamon-sugar.