Sift the flour, baking powder and salt together into a bowl.
Beat the egg, sugar, oil, milk, cinnamon and vanilla with an electric mixer* for 1 minute.
Add dry ingredients to wet ingredients and fold with a wooden spoon until just incorporated.
Add apples* to the batter and fold gently.
Fill a lined cupcake/muffin tray till 3/4th full.
Bake for 20 minutes or until a toothpick inserted comes out clean.
Allow the muffins to cool for 10 min before you tuck into them!
Notes
*You could use 3/4th of an apple (and use the leftovers as a snack while you wait for the muffins to cook!) but I would suggest not going beyond 3/4th of an apple.