Step 1: Preheat and Prepare
Preheat oven to 160°C (320°F) for a fan oven, or 175°C (347°F) for a conventional oven.
Line the base of an 8x3 inch round cake tin with parchment paper. Do not grease the sides.
Step 2: Separate the Eggs
Carefully separate the egg whites and yolks into two clean bowls.
Let them sit at room temperature for 10 minutes.
Step 3: Whip Egg Whites
Using a mixer, beat the egg whites on low speed until foamy.
Gradually add the white sugar while increasing to medium-high speed.
Beat until stiff peaks form.
Step 4: Beat Yolks and Combine Dry Ingredients
In another bowl, beat the egg yolks, powdered sugar, vanilla extract, and warm water until pale and thick (ribbon stage).
Sift in the cake flour and baking powder, folding gently with a spatula.
Step 5: Add Oil and Fold in Egg Whites
Gently fold in the vegetable oil until incorporated.
Add the whipped egg whites in three additions, folding carefully after each to maintain air in the batter.
Step 6: Bake
Pour batter into the prepared tin.
Tap the tin lightly on the counter to release air bubbles.
Bake for 35–40 minutes, or until a toothpick inserted in the center comes out clean.
Step 7: Cool and Serve
Invert the cake (while still in the tin) onto a cooling rack.
Allow it to cool completely before removing.
Slice and serve with jam, cream, and fresh fruit, or dust with powdered sugar.