Preheat oven to 325°F (160°C) and prepare a 9-inch round cake pan by greasing and flouring it or lining with parchment paper.

Separate eggs, placing whites in a clean mixing bowl and yolks in a separate medium bowl.

Whisk egg yolks with half the granulated sugar until pale, then stir in oil, milk, and vanilla; gently fold in sifted flour, baking powder, and salt.

Beat egg whites on medium until foamy, then gradually add remaining granulated sugar and beat on high until stiff, glossy peaks form.

Gently fold one-third of the whipped egg whites into the yolk batter to lighten it.

Carefully fold in the remaining egg whites in two additions, using a sweeping motion to avoid deflating the meringue.

Pour batter into the prepared pan, tap to release air bubbles, and bake for 30-35 minutes until a wooden skewer comes out clean.

Invert the cake pan immediately onto a wire rack and let it cool completely upside down.

Chill a large mixing bowl and whisk attachment for 10-15 minutes, then add very cold heavy cream, powdered sugar, and vanilla extract; beat until firm peaks form, gently folding in stabilizer if used.

Slice the cooled cake horizontally into two or three layers with a serrated knife.

Place one cake layer on a serving plate, spread a generous layer of whipped cream, and arrange fresh fruit or drained mandarin oranges over it.

Repeat with the next cake layer, cream, and fruit; top with the final cake layer.

Liberally frost the entire cake with the remaining whipped cream, smoothing the sides and top with an offset spatula, and decorate with more fresh fruit as desired.

Refrigerate the cake for at least 30 minutes before serving to allow the cream to firm up.