Apple Clafoutis

Preheat the oven to 400 degrees F (200 degrees C).

Make custard: Mix eggs and brown sugar in a large bowl until smooth. Whisk in flour and salt. Slowly add milk, stirring constantly until well combined. Stir in vanilla and set aside to rest.

Prepare apples: Melt butter, brown sugar, and water in a 10 1/4-inch cast iron skillet over medium-high heat. Stir frequently until mixture starts to boil. Reduce heat to medium; swirl the skillet, but do not stir, until mixture starts to thicken, about 2 minutes. Add apples and cinnamon. Cook and stir until apples are crisp-tender and starting to brown, 15 to 18 minutes. Remove from heat.