In a large mixing bowl, whisk together the 7 egg yolks with ¾ cup of the caster sugar until the mixture becomes thick, pale, and slightly creamy. Add the canola oil, water, vanilla essence, and salt. Mix until smooth and well combined.

Sift the cake flour and baking powder together into a separate bowl. Gradually add the dry ingredients to the egg yolk mixture, stirring gently with a spatula or whisk until the batter is smooth and lump-free. Do not overmix.

In a clean, grease-free mixing bowl, beat the 7 egg whites with cream of tartar using a hand or stand mixer. Once soft peaks begin to form, gradually add the remaining ¾ cup of caster sugar. Beat on high speed until stiff, glossy peaks form. This is key to giving the chiffon cake its airy texture.

Take about a third of the whipped egg whites and gently fold them into the yolk-flour batter to lighten it. Then, fold in the remaining egg whites carefully using a spatula. Use a gentle folding motion—do not stir or beat, as you want to keep as much air in the mixture as possible.

Pour the batter into an ungreased 10-inch tube pan. Tap the pan gently on the counter to release any large air bubbles. Bake in a preheated oven at 325°F (165°C) for 55 to 60 minutes, or until a toothpick inserted into the center comes out clean.

Once baked, immediately invert the pan and let the cake cool upside down in the pan. This prevents it from collapsing. Let it cool completely before running a knife around the edges and removing it from the pan. Slice and serve plain, or dust with powdered sugar or top with whipped cream and fruits if desired.