Preheat oven to 375 degrees
Mix together flour, salt, baking soda, and baking powder in large bowl
In separate bowl, beat butter, sugar, and eggs. Add in apples, then slowly blend in flour mixture
Put in 12 greased muffin pans
Add topping to the top of muffins
Bake 20 minutes
Once cooled, freeze in freezer bags for up to 6 months