Preheat oven to 350 F. Line a muffin tin with muffin liners. Lightly spray the inside of the liners with cooking spray. (This makes is so much easier to peel the liner away from the muffin when you are hungry!)
In a mixing bowl, combine brown sugar, oil, egg and vanilla and blend well with a fork or whisk. Add flour, baking soda,8 salt, cinnamon and nutmeg, and mix well with a wooden spoon. Stir in apples and buttermilk to combine with the other ingredients.
Distribute the batter into the prepared muffin tins. Then divide the crumb topping evenly over the top of each muffin.
Bake for 18-20 minutes, or until the center of the muffin springs back when touch with your finger. Remove from oven and serve warm or cool and freeze or refrigerate until later.