Melt butter in the microwave. Sift the cake flour.
Break the eggs into a bowl and beat. Add the granulated sugar in 2 to 3 batches, while beating with a handheld mixer. Beat until thick and creamy - when you pick up the mixer, the mixture should fall in a thick ribbon from the beaters.
Add the yogurt and yuzu peel from Step 1 and mix it in quickly with the handheld mixer. Mix the cake flour in using a rubber spatula. Add the melted butter, mix it in until the batter is smooth.
Butter the cake pan if needed, pour in the batter and bake in a 170°C oven for 35 minutes. Check for doneness with a bamboo skewer.
Story Behind this Recipe
I wanted to bake a cake using the yuzu someone had given us along with some leftover yogurt.
This cake gets puffy due to the eggs, so use fresh eggs and beat thoroughly.