Preheat oven to 320 Degree F. Line a bread tin using a grease proof paper and spray cooking spray generously or you can use round tin too.
In a large bowl, whisk together flour, granulated sugar, baking powder, salt and set aside.
In a separate small bowl, whisk together the egg, buttermilk, sour cream, oil, and vanilla.
Add the wet mixture to the dry, mixing lightly with with a whisk. The batter should be lump free and smooth.
Now pour the into the cake tin and bake in the middle rack for 30-35 mins. The colour will change slightly.
Once baked let it cool for 30 mins. Glaze, cut into pieces and serve.
Sour cream can be replaced with thick yogurt.
For the glaze take 2 tbsp of icing sugar. Add 2-3 drops of water and few drops of vanilla essence and your glaze is ready.