Combine the grated apple, grated zucchini, mashed banana, egg, buttermilk, oil and vanilla paste in a large bowl and mix until well combined.
Add in the dry ingredients and incoporate until no dry patches are visible.
Add the peeled, chopped apple and stir through.
Fill 15 muffins holes with the mixture.
Mix the cinnamon and sugar together for the topping. Sprinkle over the tops of the muffins and bake for 20 minutes at 180 degrees celsius testing with a skewer for doneness.
Allow to cool in the pan for 10 minutes before removing to a wire rack to cool completely.
Notes
Oven temps. I use a fan forced oven in Australia. I preheat my oven for 20 minutes minimum before baking. Buttermilk: you can make your own by adding 1 teaspoon vinegar to a cup of milk and leaving sit for 5-10 minutes.Self raising flour: already contains a rising agent. If you don't have this flour- the ratio for adding baking powder is 2 tsps baking powder to one cup of flour.Muffin tin: I used a nonstick one and didn't need to line it. If you don't have a nonstick pan, use cake liners.Freezing: freezing these is simple. Freeze on a tray until solid and then transfer to a container.Fridge: in the fridge in a sealed container for up to 3 days.