To prepare the water apple cake, first sift the flour into a mixing bowl, then add the baking powder and sugar. Whisk the dry ingredients together using a hand whisk.
While continuing to whisk, slowly pour in the water, strained orange juice, and vegetable oil in a steady stream. Add the grated orange zest and stir until smooth and well combined.
Wash the apples thoroughly and, without peeling them, cut them into wedges and then dice into bite-sized chunks. Add the diced apples to the batter and stir until evenly incorporated.
Pour the batter into a 22 cm (about 9-inch) cake pan lined with parchment paper.
Bake in a preheated conventional oven at 180°C (350°F) for approximately 60 minutes, testing doneness with a toothpick inserted into the center. Once baked, remove from the oven and allow to cool completely before serving.
