Preheat oven to 375°
Line a muffin tin with 12 liners
Coat chopped apples with almond flour and 1 teaspoon cinnamon
In a medium mixing bowl, mix together baking powder, 2 teaspoons cinnamon and 2 cups flour
In a separate mixing bowl, beat brown sugar and butter together thoroughly
Add vanilla extract and 2 eggs to the sugar/butter mixture and beat until combined
Add half and half and beat until combined
Slowly add in flour mixture until fully incorporated
Fold in chopped apples
Divide evenly into 12 muffin liners in muffin tin
To make the topping, combine Grape-Nuts cereal, brown sugar, cinnamon, and melted butter in a mixing bowl
Sprinkle over the unbaked muffins and press lightly into batter
Bake for 30-35 minutes
Allow muffins to cool for about 15 minutes