I tasted one of these before I stuck them all in the freezer and they weren't bad. I would suggest just leaving the topping off though. It didn't do anything for the muffins and didn't really add any flavor or anything.
2 cups flour
1 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
1/2 cup applesauce
1/2 cup brown sugar, packed and a little heaping
1 tsp vanilla
1/2 tsp cinnamon
6 medium apples, finely chopped
1/3 cup brown sugar
1/2 cup oatmeal
1 tsp cinnamon
Combine flour, baking soda, baking powder, salt and cinnamon in a large bowl. Then, mix together brown sugar, eggs, vanilla, and applesauce. Add diced apples to flour mixture and pour the applesauce mixture into the dry ingredients. Stir to moisten the dough.
Fill muffin tins 3/4 way full. Mix together topping of oatmeal, brown sugar, and cinnamon in small bowl, and spoon onto tops of muffins. Bake in preheated oven at 375 degrees for 15-20 minutes, until muffins are golden brown. Allow to cool in tin for 10 minutes before removing to cool completely.