Step 1

Preheat the oven to 180C. Set 10 paper muffin cases in a large muffin tray.

Step 2

Beat butter and sugar with electric beaters until pale and fluffy. Add yolks one at a time, beating well. Beat in zest and juice.

Step 3

Sift flour and baking powder together. Fold into mix, alternating with yoghurt.

Step 4

Whisk eggwhites in a clean bowl to firm peaks, then fold into mix. Fill cases.

Step 5

Bake for 30 minutes or until a skewer inserted in the centre comes out clean. Cool on wire rack.

Step 6

Mix icing sugar with a little extra juice to make a thick icing. Spread on cakes, add berries and leave to set.