1. **Prepare the Oven** Preheat oven to 160°C (320°F). Line the bottom of an 8-inch (20 cm) round pan with parchment paper. Do not grease the sides.2. **Make the Egg Yolk Batter** In a bowl, whisk 4 egg yolks with 30 g sugar until pale and creamy. Add oil, milk, and vanilla extract, then mix well. Sift in flour and salt, whisk gently until smooth.3. **Whip the Egg Whites** In a clean bowl, beat 5 egg whites with cream of tartar until foamy. Gradually add the remaining sugar (120 g), whipping until stiff peaks form.4. **Combine Mixtures** Gently fold whipped egg whites into the yolk batter in 3 parts, using a spatula to keep the batter airy.5. **Bake the Cake** Pour the batter into the prepared pan, tap lightly to remove bubbles, and bake for 45–50 minutes until golden and springy to the touch.6. **Cool the Cake** Turn the pan upside down and let the cake cool completely to prevent collapsing. Once cooled, release from the pan and dust with powdered sugar or serve with whipped cream and fruit.
Notes
- Always use cake flour for best texture. - Do not overmix, folding gently keeps the cake fluffy. - Cool the cake upside down to avoid shrinking. - Variations: add lemon zest, matcha powder, or cocoa for different flavors.