Step 1

Preheat oven at 350ºF / 180ºC.

Step 2

Spray or butter a 10x4-inch (27x9cm) loaf cake pan and line with a strip or parchment paper.

Step 3

In a large bowl beat sugar, yogurt, sour cream, oil, eggs, half the lemon and lime juices, zest, and vanilla for 1-2 minutes.

Step 4

Add dry, sifted ingredients (flour, baking powder, and salt) in 2 parts and beat just to incorporate well. Don't overbeat or the cake will be tough.

Step 5

Pour batter into the prepared pan and bake for 45-50 minutes, until a toothpick inserted comes out clean. The surface will be shiny and possibly cracked, not as dry as regular cakes.

Step 6

Let cool on a wire rack and unmold carefully.

Step 7

Beat powdered sugar with remaining citrus juice until no lumps remain. Add juice in batches so you make it as dense or runny as you wish.

Step 8

Pour over room tº cake and decorate with zest before it hardens.