Preheat over to 400 degrees F.
Lightly grease 12 muffin cups or line with paper muffin liners
Stir together flour, baking powder, sugar, cinnamon and salt.
In a separate bowl, stir together milk, egg and butter.
Stir egg mixture into flour mixture just until combined.
Fold in chopped apples.
Spoon batter into prepared muffin cups.
Bake for 20 minutes, or until a toothpick inserted into center of muffin comes out clean.