Preheat the oven to 200°C, 390°F, or 180°C fan. Set the oven rack in the center so the loaf bakes evenly.
Prepare a 21.5 x 11.5 x 7 cm, approximately 8.5 x 4.5 x 2.75 inch loaf pan. Lightly spray it with canola oil, then line the base and long sides with one piece of parchment paper, leaving a little overhang on the sides. There is no need to line the short ends.
For the topping, combine the Demerara sugar and cinnamon in a small bowl and set it aside.
Prepare the cinnamon apples next. Toss the apples with the cinnamon apple ingredients in a bowl and leave them to rest while you make the batter. The sugar will draw a little moisture from the apples, and that is exactly what we want.
For the batter, whisk all of the dry ingredients together in one bowl. In another bowl, whisk the wet ingredients until combined. Pour the wet mixture into the dry ingredients and whisk gently, just until you have a smooth batter. Add the prepared apples, along with all of their juices, and stir in the walnuts. The finished batter should be thick and easy to spoon, not thin enough to pour in a steady stream and not so stiff that it resembles sticky bread dough.
Spoon the batter into the prepared loaf pan and gently smooth the surface.
Now arrange the apple topping. Take about one-quarter of the apple slices and fan them slightly so they overlap, then arrange them over the loaf. Repeat with two more portions, using enough slices to cover the surface. You will likely need only about three-quarters of the apple. Finish by sprinkling the cinnamon sugar evenly over the top.
Bake for 60 minutes. Loosely cover the loaf with foil, then continue baking for another 25 minutes, or until a skewer inserted into the center comes out smooth.
Let the loaf rest in the pan for 15 minutes. Then carefully use the parchment overhang to lift it out and transfer it to a wire rack. Give it at least 1 hour to cool on the rack before slicing. A little patience here makes all the difference.
This apple bread is moist and full of flavor, so it is lovely served just as it is. If you want something a little more indulgent, lightly toast a slice and spread it generously with butter.
If your loaf pan is a little larger than the one specified, that is perfectly fine. Just keep in mind that the finished loaf will not be quite as tall as the one pictured.
For leftovers, the loaf stays fresh for up to 5 days. Keep it in the fridge and warm individual slices before serving, either in the microwave or by toasting them gently in the oven or toaster. The loaf can also be frozen for up to 3 months.