Preheat oven to 180ºC
Grease a loaf tin
Scoop yoghurt out into a large bowl, add eggs, oil and sugar.
Sift flour, baking powder and salt into bowl and mix well.
Stir in grapefruit juice and zest.
Spoon into a prepared loaf tin and smooth the top with the back of a spoon.
Bake for 30 to 35 Minutes until a tester comes out clean.
Turn out onto a cooking rack and cool completely before topping with drizzle and serving.
Combine icing sugar and grapefruit juice and zest. Mix well.
Drizzle over cooled cake, before slicing.