Preheat oven to 220°C (430°F) or 200°C (390°F) for fan-forced ovens. Line a 24-hole muffin tin with paper cases and spray the inside of the cases generously with oil to prevent the muffins from sticking.Roughly chop and peel (optional) apples into little cubes.
For the dry ingredients - In a large bowl, place in the flour, baking powder, baking soda, cinnamon and salt. Whisk the dry ingredients well to combine.
For the wet ingredients - In a separate bowl, pour in the buttermilk and oil, then add in the eggs, sugar and vanilla extract, then whisk well to combine.
Make a well in the dry ingredients, then pour in the wet ingredients. Fold the mixture until almost combined, then add the apples. Fold a few more times until no dry bits are showing, but don't over-mix the batter.
Divide the batter evenly into the prepared muffin tin. Mix the demerara sugar and cinnamon together in a small bowl, then sprinkle the sugar mixture over the muffins. Bake for 18 to 20 minutes, or until a skewer comes out clean when inserted in the middle of a muffin.
Notes
(NOTE 1) Apples - Peeled or unpeeled red or green apples would work in these muffins. I didn't peel my apples, as I don't mind eating their skin.(NOTE 2) Plain flour (All-purpose flour) doesn't have any leavening (raising agents) such as baking powder mixed in.(NOTE 3) Buttermilk - No buttermilk in your fridge? Make 1 cup of buttermilk substitute by mixing 1 cup of milk with 2 tablespoons of vinegar or lemon in a jug/bowl. Cover and refrigerate for at least 30 minutes, the milk should thicken slightly. Give it a quick stir before using.(NOTE 4) Mild or light Olive oil - I love extra virgin olive oil, but it has a strong flavour and may overwhelm the muffins. To still get the goodness of olive oil, I used light olive oil for a more neutral taste. You could also swap olive oil for vegetable or canola oil.(NOTE 5) Demerara sugar is a form of raw sugar. Its crystals are larger, coarser and darker than regular white sugar with a subtle molasses flavour. You could swap raw sugar or turbinado sugar for demerara sugar.Leftovers - Allow the Apple Cinnamon Muffins to cool completely at room temperature, then transfer them into an airtight container and store them at room temperature for up to 3 days. If humid, store them in the fridge. When frozen they'll keep for 3 months.I've used a third-party application to calculate the calories and nutritional information, so please use this as an approximate guide only.Cooking measurements are in Australian standard spoon and cup measurements. For specific details and conversions, visit ourAustralian Cooking Measurements page.