Step-by-Step Instructions

Prepare Dry Ingredients:

Sift together flour, potato starch, and baking powder in a bowl. Set aside.

Cream the Butter and Sugar:

Beat the softened butter with powdered sugar, vanilla seeds, lemon zest, and orange zest using an electric whisk until light and fluffy.

Add Egg Yolks:

Gradually mix in the egg yolks one at a time, ensuring each is fully incorporated.

Whisk Whole Eggs and Granulated Sugar:

In a separate bowl, whisk whole eggs with granulated sugar until pale and frothy.

Combine Mixtures:

Alternately fold the egg-sugar mixture and dry ingredients into the butter mixture using a spatula. Repeat until fully incorporated, resulting in a smooth, airy batter.

Prepare the Mold:

Butter and flour the cake mold to prevent sticking. Pour in the batter and smooth the top with a spatula.

Bake:

Preheat the oven to 340°F (170°C). Bake for 45-50 minutes, checking with a toothpick around 30 minutes. Cover with foil if browning too quickly.

Cool and Dust:

Allow the cake to cool in the mold for 20 minutes. Turn it onto a rack to cool completely. Dust with powdered sugar before serving.

Variations and Tips

Gluten-Free: Replace type 00 flour with an equal amount of rice flour.

Dairy-Free: Substitute butter with an equivalent amount of vegetable oil, emulsified with the egg yolks.

Filling Options: Add a layer of buttercream, jam, or mascarpone cream for an extra treat.

Storage: Store in a covered container for up to 3 days or freeze without powdered sugar.