Preheat the oven to 350°F. Line a muffin/cupcake tray with liners.
Add all the dry ingredients to a medium or large bowl. Mix until there are no lumps. Add all of the wet ingredients to the bowl (except the apple) and mix until just before it's combined. Add the chopped apple and fold until the apple is evenly dispersed.
Use an ice cream scoop or a large spoon to divide the batter into your muffin tin.
Optional: Scatter the remaining chopped apple and granulated coarse sugar on top.
Bake the muffins in the oven for 20-25 minutes OR until a skewer can be inserted into the middle and there is no wet batter on it, though some crumbs are fine (note 3).
Cool the muffins in their tray for 10 minutes then allow them to cool on a wire rack.
Enjoy the muffins warm or at room temperature! The muffins can be stored in an airtight container at room temperature for 2 days, in the fridge for 3 days or in the freezer up to 1 month. The crunchy raw sugar topping will soften after 1 day.