Preheat the oven to 355 degrees F (180 degrees C).
Add the Lemon Juice (1 teaspoon) to the Water (150 milliliter). Add the Red Apple (1) about 2mm thickness. Save the other half of the apple.
Place the sliced apples into the bowl of lemon water. Microwave, about 1-2 minutes until the apples are pliable, soft but not mushy. Reserve 1 tablespoon apple liquid to grated apple.
Drain the apple slices and dry them with kitchen towel.
Add Red Apple (50 gram) in a bowl and mix well with 1 tablespoon apple liquid.
Separate Egg (4) yolks and whites and set both aside.
In a large bowl, stir well 3 egg yolks, Vanilla Extract (1/2 teaspoon), and Caster Sugar (25 gram) with a hand whisk. Add grated apple and Corn Oil (40 milliliter), stir well again to combine. Sift in Cake Flour (75 gram) and mix well.
Whisk 4 of the egg whites, Caster Sugar (50 gram), and Lemon Juice (1 teaspoon) till frothy with an electric mixer at low speed, gradually add in the sugar in batches. Continue beating egg whites at medium speed till stiff peaks form.
Add ⅓ of the egg whites into egg yolk mixture, fold well with a rubber spatula. Then gently fold in the rest of egg whites till combined.
Pour batter into a 7 inch removable cake pan. Gently arrange sliced apples on top of the batter into a rose form.
Bake in preheated oven for 15 minutes.
Then lower temperature to 320 degrees F (160 degrees C) and bake for another 35-40 minutes.
Invert the cake pan immediately to cool completely before removing the cake from pan