Step by step

1. Preheat oven to 175ºC. Line a 23 cm cake pan pan with parchment paper so that it covers the bottom and goes up the sides of the pan. Fold parchment paper so that it hugs the sides of the pan, like an upside down hat. Spray with non-stick spray.

2. With a sharp paring knife, slice ends of oranges and grapefruit. Following curve of fruit, cut away peel, removing as much white pith as possible. Slice oranges and grapefruit crosswise into 0,5 cm-thick rounds and remove any seeds; set aside. Slice kumquats into 0,5 cm-thick rounds and remove any seeds; set aside.

3. Attach the Sifter Attachment (without Sifter Assembly) to your Stand Mixer (with Whisk Attachment), and press "Tare" to zero scale. Add 100 g of brown sugar to ingredient hopper and weigh. Add brown sugar into Stand Mixer bowl through chute.

4. Melt 110 g of butter, pour over brown sugar and stir until the sugar begins to dissolve. Spread mixture over the bottom of the prepared cake pan, then line the bottom with prepared citrus fruits. Set aside.

5. Add 65 g of brown sugar and 75 g of granulated sugar to the ingredient hopper and weigh, pressing "Tare" between each ingredient. Add sugars into stand mixer bowl through chute. Add 225 g of butter and beat the butter and sugars together on speed 6 until light and fluffy. Add in the eggs, orange juice, orange zest, and vanilla extract. Mix until combined.

6. Remove whisk attachment and attach beater attachment. Add Sifter Assembly to Sifter Attachment.

7. Add and weigh the flour, baking powder, baking soda, cardamom and salt to the ingredient hopper, pressing "Tare" between each ingredient. Give hopper ingredients a stir to combine. Turn Stand Mixer to speed 2 and sift dry ingredients into stand mixer bowl, slowly adding in yogurt as well. Mixture will be thick.

8. Pour the batter over the prepared citrus slices, spreading it evenly to the edges.

9. Bake for 35 minutes, then allow to cool completely before inverting onto a serving tray.