Light and Airy Chocolate Chiffon Cake

1. Preheat oven to 320F. 
2. Using a microwave, warm oil for about 30-40s until warm to touch. In a mixing bowl, add in the warm oil, sift in flour and cocoa powder and mix well. 
3. Add in milk and mix well, and then egg yolk and mix until well combined.
4. In a stand mixer with a whisk attachment, whisk egg whites and lemon juice. While whisking, when egg whites start to form bubbles, slowly add in the sugar in 3 intervals. Whisk the egg whites until stiff peak. The tip of the meringue should be straight up and shiny when you hold up the whisk.
5. Fold the egg white into the yolk batter in 3 intervals until well incorporated. Pour batter into the chiffon cake pan. Tap the pan on a flat surface 3 times to release some air bubbles.
6. Place the pan with the batter into a slightly bigger pan, and then followed by another pan. Fill the outermost pan with water, just enough to cover the surface of the pan. 
7. Bake in the lower/middle rack of the oven for 75-80 mins. At the 20min mark, take out the chiffon cake and quickly slit the top. Place it back in the oven and continue baking. The slit step is so that the top blooms out evenly.
8. Once done, remove from the oven and immediately tap it on a flat surface to remove the big hot air bubbles. Quickly invert it upside down and let it cool completely (about 1-2 hours). 
9. Once the cake has completely cooled, remove the cake from the pan with the bottom of the cake facing on top. Slice and enjoy!