Prepare the crepe batter: In a bowl, whisk together the flour, eggs, milk, sugar, vanilla extract, and salt. Stir in the melted butter until smooth.
Cook the crepes: Heat a non-stick skillet or crepe pan over medium heat. Lightly grease with butter or cooking spray. Pour 1/4 cup of batter into the pan and swirl to coat the bottom evenly. Cook for 1-2 minutes on each side, or until lightly golden. Repeat with the remaining batter.
Make the apple cinnamon filling: In a skillet, melt butter over medium heat. Add the sliced apples and cook until soft, about 5-7 minutes. Stir in the brown sugar, cinnamon, and nutmeg (if using). Continue to cook until the apples are tender and caramelized.
Assemble the crepes: Place a crepe on a plate, spoon some of the apple cinnamon mixture into the center, and fold the crepe. You can also roll it up if preferred.
Optional toppings: Serve with whipped cream, maple syrup, or a dusting of powdered sugar.
Serve: Enjoy your delicious apple cinnamon crepes warm!