Preheat oven to 180C. Grease and flour an 10x20cm loaf tin. In a medium bowl, mix flour, baking powder and salt together and set aside.
In a large bowl, cream the butter and 1 cup sugar until light and fluffy. Add eggs and beat well. Mix in the juice of 1 lemon. Add the flour mixture, alternating with the milk. Fold in the lemon zest and blueberries. Pour into prepared loaf tin.
Bake for 60 to 70 minutes, or until a toothpick inserted into the loaf comes out clean. For the glaze, combine 1/4 cup sugar with 2 tablespoons lemon juice. Drizzle over cake while still warm.