Preheat the oven @180'c for 10 minutes. Grease and dust or line a loaf pan with some parchment paper. I've used a 7-inch loaf tin here. ( I have used a weighing scale for the ingredients, and have mentioned approx measurements in cups/ spoons too wherever possible as per US metric conversions )

Take 1/4 tsp flour in a bowl and add the blueberries to this bowl. Coat the berries with the flour. 

In a large mixing bowl, sift together flour, baking powder, baking soda, and salt. Set it aside. 

In another mixing bowl, beat together butter and sugar until pale and fluffy. Next add the vanilla extract, lemon zest, lemon juice, and the milk. Beat again to incorporate everything. 

Now add the sifted flour mixture in parts and gently fold the wet ingredients with the dry. Do not over mix. This batter is a bit thick. If you feel it is too thick, you can add 1-2 tsp of milk. However, I didn't add any. 

Next, add the berries to the batter and give one last fold. Pour the batter in the tin and bake for approximately 40 minutes or until a skewer inserted in the center of the cake comes out clean. Let the cooldown on a cooling rack for a minimum of 25-30 minutes before demolding and slicing. 

This cake stays fresh for 3-4 days at room temperature in an airtight box. You can even refrigerate the cake after it has cooled down, simply microwave it for 10 seconds before serving a slice. It will be as good as fresh and super soft too. 

For the frosting, I mixed together powdered sugar with the lemon juice. Make sure it is not too runny. Pour it over the cake only after it cools down completely.