Beat the butter with the sugar until you have a creamy mixture. Add the yolks and the zest. Mix well. Add the flour together with the baking powder, alternating with the milk.
Pour into an 8 in (22 cm ) tall removable round bake pan. We recommend using the Instant Vortex Round Cake Pan.
On the Instant Vortex control panel, press Bake and then set time to 20 Minutes and temperature to 325˚F (163˚C). Press Start.
Combine all the ingredients and put the filling on the dough.
On the Instant Vortex control panel, press Bake and then set time to 10 Minutes and temperature to 325˚F (165˚C). Press Start.
Once ready, let cool and serve with whipped cream if desired.