Preheat the oven to 325°F (165°C). Line the bottom of a 9-inch round cake pan with parchment paper and leave the sides ungreased.

In a medium bowl, whisk the egg yolks with 1/4 cup of the granulated sugar until pale and fluffy, about 2 minutes.

Whisk in the vegetable oil, whole milk, and vanilla extract until smooth.

Sift the cake flour, baking powder, and salt into the yolk mixture and gently stir until just combined with no flour streaks.

In a clean bowl, beat the egg whites with the cream of tartar on medium speed until soft peaks form, about 3 minutes.

Gradually add the remaining 1/4 cup granulated sugar while beating on medium-high speed until stiff, glossy peaks form, 2–3 minutes.

Fold one-third of the beaten egg whites into the batter to loosen it, then gently fold in the remaining whites in two additions until no white streaks remain.

Pour the batter into the prepared pan, smooth the top, and bake for 35–38 minutes, until golden and the top springs back when lightly touched.

Cool the cake in the pan for 5 minutes, run a thin knife around the edges, invert onto a cooling rack, remove parchment, and let cool completely.

Dust with powdered sugar just before serving.