1. Heat the oven to 180C/160C/gas 4. Grease and line a 20cm loose-bottomed cake tin. In a large bowl, stir together the flour, Dr. Oetker Baking Powder and caster sugar.
2. In a jug, whisk together the eggs, soured cream, lemon zest, juice and oil. Add the egg mixture to the dry ingredients and mix thoroughly until evenly blended. Pour into the prepared cake tin and bake for about 1 hr, until well the cake is risen and firm to the touch (a skewer inserted into the centre should come out clean).
3. To make the drizzle, mix the icing sugar and lemon juice in a small saucepan, stirring over a low heat until it comes to the boil. Let it boil for 2 mins until it becomes syrupy. As soon as the cake comes out of the oven, prick the surface with a metal skewer, then pour over the drizzle, covering the top of the cake. Leave the cake to cool completely in the tin.
4. Once cool, sprinkle over the lemon zest and enjoy!