Preheat the oven to 170°C (340°F). Grease and line an 18cm (7-inch) round cake pan with parchment paper.
In a medium bowl, sift together the Japanese cake flour and baking powder. Set aside.
In a large bowl, whisk the egg yolks with 50 grams of granulated sugar until the mixture becomes pale and slightly thickened.
Add the vegetable oil, whole milk, yuzu juice, and lemon zest to the egg yolk mixture. Whisk until fully combined.
Gradually fold the sifted flour mixture into the wet ingredients until just combined. Do not overmix.
In a separate clean bowl, beat the egg whites with the cream of tartar using an electric mixer on medium speed until foamy.
Gradually add the remaining 50 grams of granulated sugar to the egg whites while continuing to beat until stiff, glossy peaks form.
Gently fold one-third of the beaten egg whites into the batter to lighten it. Then carefully fold in the remaining egg whites until no white streaks remain.
Pour the batter into the prepared cake pan and smooth the top with a spatula.
Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and let it cool in the pan for 10 minutes. Then transfer it to a wire rack to cool completely.
Once cooled, dust the top of the cake lightly with powdered sugar before serving.