Preheat Oven:
Preheat oven to 350°F (175°C) and line a 12-cup muffin pan with cupcake liners.

Make Cupcake Batter:
In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In a large mixing bowl, beat softened butter and granulated sugar until light and fluffy (2–3 minutes).
Add eggs one at a time, mixing well. Stir in vanilla.
Alternate adding dry ingredients and buttermilk, starting and ending with dry. Fold in chopped apples.

Make the Crumble:
In a small bowl, combine oats, flour, brown sugar, and cinnamon. Add melted butter and stir until crumbly.

Assemble:
Divide cupcake batter evenly into liners, filling about ⅔ full. Top each with a spoonful of crumble mixture.

Bake:
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan for 5 minutes, then transfer to a wire rack.

Drizzle with Caramel:
Once cooled, drizzle caramel sauce over each cupcake.