Heat oven to 180°C.
Grease a Bundt tin and dust with flour.
Add lemon juice to milk (it will curdle, this is fine).
In electric mixer, whisk butter until creamy. Add sugar and beat until pale and fluffy.
Add eggs one at a time, beating after each one.
Sift dry ingredients. Add blueberries and mix gently to cover.
With spoon, fold in half of the flour, then half of milk into batter; repeat.
Spoon into Bundt tin and smooth off top with the back of a spoon.
Bake for 30 to 35 minutes, until golden brown. Start 30min timer
Remove from tin carefully. Place a wire cooling rack over the top of the tin, Flip the wire wrack and the tin over. Remove the cake tin and allow to cool completely.
You will ice the smooth “bottom” of the cake.
Beat butter and icing sugar together well before adding lemon juice and zest.
Spread onto cooled cake. Decorate with blueberries and some more lemon zest.