Sift the flour into a bowl and set aside.
Preheat oven to 350 F (176 C)
In a mixing bowl, cream the butter until smooth.
Add the sweetener, and then eggs (one at a time) and vanilla extract. Mix well.
Add the baking powder, cinnamon and salt to the flour and whisk.
Add the flour and the milk to the creamed butter mixture, alternating a couple of scoops of flour followed by the milk and repeat until both the flour and milk are well mixed.
Add the chopped apples and stir into the batter. *Reserve a few pieces of apple to top the muffins with, if desired.
Divide the batter between 12 muffin tins. (line with paper liners for less mess)
Top each muffin with a piece or two of the remaining chopped apple.
Bake in the oven for 18-20 mins or until golden. A toothpick should come out clean when inserted, indicating that they are fully baked.
Once baked, remove from the pan and allow to cool on a wire cooling rack.