Blend butter, sugar and eggs until smooth. Add buttermilk, salt, apples and mix. Stir in flours, baking soda and cinnamon, stirring only to moisten. Spoon into a greased muffins tin and sprinkle with topping. Bake at 375 degrees for 20 minutes.
Recipe by The Domestic Blonde at https://thedomesticblonde.com/2015/12/29/apple-cinnamon-muffins/