These are a family favorite. They do take a while to make, but they are worth it!
Combine in a large mixing bowl brown sugar, vegetable oil and egg.
Combine in a small bowl buttermilk, baking soda, salt, cinnamon and vanilla extract. You can make sour milk if you don't have buttermilk by putting 1 Tbsp. of vinegar in the bottom of a measuring cup and adding up to the 1 cup mark with plain milk.
Using a small bowl, measure out 2 1/2 cups flour.
Add milk and flour in 1/3 increments alternately to the sugar mixture, which is in the bigger bowl. Stir well with a rubber scraper after each addition.
Fold in the apple. Can fold in chopped pecans or walnuts. This is optional and I use nuts if I have them on hand. Nuts can be expensive so I make them both ways and we love them both ways.
You can either use muffin papers or spray a muffin tin. Fill the cups about 2/3 full.
Mix the topping and sprinkle a little on top of each muffin before you put them in the oven.
Bake in a 350 degree oven approximately 30 minutes.