Cream together 3 egg yolks, ½ the sugar, and lemon zest until nearly white in color. Add in sunflower oil and milk. Stir until incorporated. Do not overmix
Sift flour and baking powder into mixture. Stir until fully incorporated.
In a separate bowl, whip together egg whites, salt, and remaining sugar until soft peaks form.
Add half of the whipped egg mixture into original bowl and whip until mixture turns pale yellow.
Add the rest of the whipped egg mixture and stir to combine.
In a separate bowl, whip together mascarpone cream, 1 egg, cocoa powder, corn starch, and 50 grams of sugar, vanilla extract until completely mixed
Poor cake batter into a 9x9” cake pan lined with parchment paper and spread out evenly. Pipe chocolate cream mixture on top of cake batter making swirls and other designs to create the “marble” effect
Bake for 25-30 minutes on 356° F. Remove cake and allow to cool. Use parchment flaps to remove cake from pan and place on serving dish.
Remove parchment paper and sift powdered sugar on top of cake.
