Grease and line cake pan: Grease a 20cm / 8-inch regular cake pan or spring form pan with butter, then line with parchment / baking paper.
Preheat the oven: Preheat the oven to 180°C/350°F (160°C fan)
Peel and chop apples: Core, peel and chop the apples into ½ inch (1 ½ cm) cubes
Place apples in the cake pan: Distribute the chopped apples evenly in the cake pan
Always start by first adding the wet ingredients into the blender: Add the melted butter, eggs and vanilla into the blender. Place the lid securely onto the blender and blend the wet ingredients for only 10 seconds.
Add in the dry ingredients: Unplug your blender and add in the sugar, flour, baking powder, salt and cinnamon powder. Plug the blender back in and blend again for another 5-10 seconds. See note 5
Scrape the bottom and sides of the blender jug: Switch off and unplug the blender, then use a rubber spatula to scrape the bottom and sides of the blender jug. Using your spatula, gently mix in any remaining speckles of dry ingredients you may see at the bottom of the blender. See note 6
Pour the batter into the cake pan: Pour the batter over the apples. Gently stir ensuring that you coat all the apples pieces well with the batter. Sprinkle granulated sugar evenly over the top.
Bake: Bake for about 25 to 30 minutes or until the cake is golden, and a toothpick inserted into the center comes out clean.
Remove from the oven: Remove from the oven and allow to cool in the pan for 5 minutes then run a blunt knife around the edges to loosen.
Turn cake out onto cooling rack: Remove the sides if you are using a spring form cake pan. If you are using a regular cake pan, then gently invert the cake onto a cooling rack. Remove the parchment paper and carefully flip the cake over onto a plate or serving platter.
Sift with powdered sugar: Lightly sift powdered sugar over the cake if preferred.