Preheat oven to 350° F. Spray standard muffin pans with non-stick cooking spray and set aside.
Measure the cornmeal, flour, sugar, baking powder, and salt in a large bowl. Whisk well.
In a separate bowl, whisk the milk, apple butter and eggs together.
Pour the wet mixture into the dry mixture and whisk well.
Stir in melted butter. Add the diced apple to the mixture and mix well.
Use a scoop to fill the muffin pans two-thirds full. Bake 18-20 minutes, until golden. Cool for 2-3 minutes in the pans, then flip out muffins.